Title
Author(s)
Citation
Issue Date
Doc URL
Type
File Information
Dry Matter Production, Yield Components and Grain yield of the Maize Plant
TANAKA, Akira; YAMAGUCHI, Junichi
Journal of the Faculty of Agriculture, Hokkaido University = 北海道大學農學部紀要, 57(1): 71-132
1972-07
http://hdl.handle.net/2115/12869
bulletin
57(1)_p71-132.pdf
Instructions for use
Hokkaido University Collection of Scholarly and Academic Papers : HUSCAP
DRY MATTER PRODUCTION,
YIELD COMPONENTS AND GRAIN YIELD
OF THE MAIZE PLANT
Akira TANAKA and }unichi YAMAGUCHI
Laboratory of Plant Nutrition, Faculty of Agriculture
Hokkaido University, Sapporo, Japan
Contents
INTRODUCTION . . . . . . . . . . . . . .
I. GENERAL GROWTH PATTERN . . . .
Growth Pattern and Dry Matter Accumulation
Carbohydrate Accumulation.
Characteristics of Each Leaf . . . . . . . . .
Discussions . . . . . . . . . . . . . . . . . .
II. CONTRIBUTION OF LEAVES AT VARIOUS POSITIONS TO
GRAIN YIELD AND DRY MATTER PRODUCTION
Effect of Removing Leaves or Ears . . .
Translocation of Photosynthetic Products . . . . . . .
Discussions
III. DRY MATTER PRODUCTION, PHOTOSYNTHESIS
AND RESPIRATION
Photosynthetic Rate
Respiratory Rate . . .
Dry Matter Production Related to Photosynthesis and Respiration.
Photosynthesis and Respiration at Stratified Strata of Population .
Discussions . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV. VARIETAL TRAITS ASSOCIATED WITH YIELDING ABILITY.
Heterosis and Yielding Ability
Comparison among Varieties . . . . . . . . . . . . .
Discussions . . . . . . . . . . . . . . . . . . . . . .
V. CULTURAL FACTORS AFFECTING GRAIN YIELD
Date of Planting . . . . . . . . . . . . . . . . . . .
Interactions among Spacing, Nitrogen Level and Variety
Interactions between Climatic and Cultural Conditions.
Discussions . . . . . . . .
VI. GENERAL DISCUSSIONS
CONCLUSION . . . . .
ACKNOWLEDGMENT
REFERENCES. . . . .
[Jour. Facu!. Agr., Hokkaido Univ., Sapporo Vo!' 57, Pt. 1, 1972]
72
72
72
74
75
76
77
77
79
83
85
86
91
92
94
95
98
99
101
106
108
108
110
117
122
124
127
128
128
72
A. TANAKA AND J. YAMAGUCHI
INTRODUCTION
Maize and rice rank second and third in importance among all crops
for supplying foods to the people in the world. These two crops are
especially important for people in developing countries. Improving the
productivity of maize and rice is urgently needed to help solve world food
problems.
To improve crop production, more emphasis has been given recently
to physiology of dry matter production. Much information is being accumulated for several crops.
The authors have been studying the physiology of grain and dry matter
production of rice and published critical discussions (TANAKA, NAVASERO,
GARCIA, PARAO and RAMIREZ (1964), TANAKA, KAWANO and YAMAGUCHI
(1966)). More recently, they have been working with maize and have
published several reports in Japanese.
The object of this paper is to discuss critically the physiology of grain
production of maize in relation to the dry matter production. For this we
have used data presented in separate reports by the authors in Japanese
and data available in the literature. References to the authors' experiences
with rice are included. Detailed descriptions of experimental methods are
omitted in this paper because they are available in previous reports.
I. GENERAL GROWTH PATTERN
Since increasing production of grain is the objective of improving
maize cultivation, a general understanding of accumulation processes of dry
matter and carbohydrates in each organ during growth is a prerequisite to
discussing improvements of varieties and of cultural practices. For this
reason, the following observations were made.
Growth Pattern and Dry Matter Accumulation
Ko No. 504, a standard dent corn variety in Hokkaido, was planted in
a field of Hokkaido University with a standard cultivation method which
includes sowing by mid-May at a spacing of 50 cm x 50 cm, one plant
per hill, and applying 150 kgJha each of N, P 20 5 and K 20 (TANAKA and
ISHIZUKA (1969)). Unless stated otherwise, this cultivation method was
used in all following experiments.
Seedlings emerged about two weeks after sowing. Leaves developed in
succession with a leafing interval of about 4.5 days. Elongation of internodes began 40 days after sowing, became vigorous 20 days later and
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
73
stopped 10 days after silking.
Plant /leight
Tasseling occurred 70 days after
250
sowing and silking started two
weeks later. No tiller developed
200
(Fig. 1).
'"""
<>
An increase of the weight '-' ISO
15
......
of the leaves, the culm, and the -<::
~
.~
10 ~
cob-and-husks occurred III this :t: 100
i'?
"sequence. The weight of these
t:J
SO
<u
5 '-l
organs decreased slightly during
grain-filling. The weight of the
a
a
150
grains increased slowly for about
two weeks after silking and then
.....,
increased rapidly until growth '"'~
'""ceased.
100
<t
It took about one month for
~
the ear-primordium to complete its '-'
§
elongation after initiation. The
~
<:>
weight of the husks increased first, "-c SO
then the cob. Increase of the ....,
~
weight of these organs continued .~
~
for about two weeks after silking.
00
20
40
60
80 100 120
The weight of the grains started
Days after sowing
to increase before the weight of
t t t
the husks and the cob reached
.~
t);)
~
'" ~
.~
.l!.<:: .~
their maximum and continued to
]
6
~
~ ~
~
increase until harvest. The weight
V5
.~
'" V)
1:
tE
~
of the husks and the cob decreased
Vegetative Phase ICfO/iI-filling Phose
when the increase of the grain
Initiol
Active
Active
weight became active. The deFig. 1. Outline of growth process
crease started in the husks first
(Ko No. 504, 1967)
and then in the cob.
Based on these observations, the growth process of the maize plant
can be divided into the following four phases.
Initial vegetative phase: The leaves are initiated and then develop in
succession from the lower to the upper. The dry matter production is
slow. This phase is terminated by the initiation of reproductive organs
or by the beginning of internode elongation, or both.
Active vegetative phase: The leaves, the culm and the primordia of
"
"
I
I
Fitio/l
I
74
A. TANAKA AND J. YAMAGUCHI
reproductive organs develop. An active increase of the weight of the
leaves occurs first and then that of the culm. This phase is terminated
by silking.
Initial grain-filling phase: The weight of the leaves and the culm
continues to increase at a slower rate. The husks and the cob continue
to gain weight. The weight of the grains increases slowly. This can be
considered a transitory phase from the vegetative phase to the grain-filling.
Active grain-filling phase: A rapid increase in the weight of the
grains occurs. This increase is accompanied by a slight decrease of the
weight of the leaves, the culm, the husks and the cob.
Carbohydrate Accumulation
"Carbohydrates" is used to mean the total amount of sugars and starch.
In the vegetative organs, there was almost no starch.
The sugar content of the
Cob-and- husks
leaves was low throughout growth
(Fig. 2, top). For the culm, it
15
10
D
Culm
was low at early growth stages,
Leaves
0 •
D
started to increase before silking,
5~"--'"
•
V .--""':----'~.
Tassei7...... x'--.
increased considerably after silking,
o
reached a maximum at the end
of the initial grain-filling phase
and then decreased. The sugar
content of the cob-and-husks and
the grains was relatively high during the initial grain-filling phase,
and then decreased during the
active grain-filling phase.
Only a small amount of carbohydrates accumulated in the vegeo 20 40 60
tative organs (Fig. 2, bottom).
Days after sowing
However, the accumulation in the
Fig. 2. Fluctuation of sugar content (top)
culm and in the cob-and-husks
and amount of total carbohydrates
during the initial grain-filling phase
in the plant (battom) during growth
was significant. During the active
(Ko No. 504, 1967)
grain-filling phase, the amount of
carbohydrates in these organs decreased and the amount III the grains
increased rapidly. With a conventional substruction method described elsewhere (ISHlZUKA and TANAKA (1953)), about 90 percent of the carbohydrates
in the grains at harvest were the photosynthetic products during grain-filling.
At
~
-
75
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
Although data are not presented, the translocation of nitrogen compounds from leaves and culm to grains during grain-filling was considerable.
Characteristics of Each Leaf
Fukko No.8, a standard dent corn variety in Hokkaido, was grown
with the standard cultivation method. There were 16 leaves on the culm
and no tiller developed. Twelve leaves were alive and four leaves at the
bottom were dead at silking. A fully developed ear formed at the node
of the tenth leaf. Sometimes a second ear formed at the node of the
ninth leaf, but only limited kernels developed on it.
The length and the width of the leaves, consequently the leaf area,
increased from the lower to the upper leaves, reached a maximum at the
tenth or the eleventh leaf and then gradually decreased (Table 1). The
thickness of the leaves increased from the bottom to the top. The tenth
to twelfth leaves were heaviest. The five leaves including the one below
TABLE
I
Leaf
Leng"
posltlOn**
(em)
16
48
1.
Morphological characteristics* and nutrient
content at silking of each leaf on the main
culm (Fukko No.8, 1969)
Nutrient content
(%)
I Wid,h I
Area
Thickness
Weight
(em)
(cm 2)
(mg·dm- 2)
(g)
7.8
271
458
1.24
3.27
0.45
2.40
I
N
I
p
I
K
15
61
9.5
462
429
1.98
3.51
0.40
2.63
14
70
10.8
580
432
2.51
3.37
0.43
2.76
13
76
11.8
743
423
3.14
3.61
0.39
2.89
12
81
11.8
811
410
3.33
3.59
0.38
2.89
11
83
11.9
860
382
3.29
3.43
0.35
3.00
10
86
11.7
863
387
3.34
3.08
0.30
3.43
9
83
11.2
795
365
2.90
2.81
0.28
3.36
3.50
8
71
9.8
576
355
2.04
2.77
0.22
7
59
7.6
390
324
1.26
2.67
0.21
3.12
6
49
6.4
285
319
0.91
2.46
0.23
3.07
5
38
4.6
147
310
0.46
-
-
-
4
28
3.1
69
308
0.21
-
-
-
3
20
2.0
31
286
0.09
-
-
-
2
12
1.5
15.3
275
0.04
-
-
-
1.7
6.6
276
0.02
-
-
-
1
5.0
* Obseavations were made at growth stages when each leaf completed expansion..
** Counted from the bottom.
76
A. TANAKA AND J. YAMAGUCHI
and the three above the first ear were largest. They accounted for more
than 60 percent of the total leaf area. At silking the nitrogen content was
higher in the thirteenth leaf than in leaves above or below. The phosphorus content was highest in the' top leaf and decreased towards the
bottom leaf. Conversely, the potassium content was lowest in the top leaf
and increased in successively lower leaves, except for a few leaves at the
bottom.
Discussions
The growth process of the maize plant described here is almost identical
with that reported by HANWAY (1963). It can be divided into four phases:
initial vegetative phase, active vegetative phase, initial grain-filling phase,
and active grain-filling phase.
During the initial grain-filling phase some sugars accumulate in the
culm and the cob-and-husks. The largest accumulation in the culm is in
the internode from which the ear exerts (VAN REEN and SINGLETON (1952),
ASANUMA, NAKA and T AMAKI (1967)). The sugar content of the grains
increases during the initial grain-filling phase and then decreases during
the active grain-filling phase (EARLEY (1952)). These are indications of an
imbalance between rate of photosynthesis of the leaves and rate of starch
formation in the developing kernels during the initial grain-filling phase.
In this sense, the sugars in the culm or in the cob-and-husks are transitory.
During the active grain-filling phase, the weight of the grains increases
rapidly and the weight of the vegetative organs decreases slightly. This
suggests that there is probably some retranslocation of substances from the
vegetative organs to the grains during this phase. However, this decrease
of the weight of the vegetative organs was not observed by HANWAY (1963).
From the evidence available, it seems that this type of retranslocation does
not make a very important contribution to grain weight. This decrease is
quite large in the rice plant, at least under some circumstances (MURAYAMA,
et al. (1955)).
The sugars accumulated in the culm or in the cob-and-husks decreased
during the active grain-filling phase. The amount stored in the vegetative
organs and then translocated to the grains accounts for less than 10 percent
of the total carbohydrate accumulated in the grains at harvest. Although
the amount of sugars stored in the culm is not large, this transitory sugar
is important to maintain a constant kernel growth rate irrespective of daily
fluctuations in the rate of photosynthesis (DUNCAN, HATFIELD and RAGLAND
(1965)). In the rice plant, the growth rate of grains is higher in the day
time than at night (MA TSUSHIMA, OKADA and W ADA (1957)).
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
77
More than 90 percent of the weight of the grains is derived from the
product of photosynthesis during grain-filling and is translocated to the grains
directly. Therefore, dry matter production after silking is important for
grain production. The five leaves at or just above the ear are probably
most important during grain-filling.
In several ways the growth of the maize plant described here is similar
to the growth of the rice plant (IsHIzuKA and TANAKA (1953), ARASHI
(1954), TOGARI, et al. (1954), TANAKA et al. (1964), ISHlZUKA (1965),
MURAYAMA (1955, 1965)). Major differences between rice and maize are: (1)
maize does not tiller as actively as rice and (2) in rice some starch or sugars are
accumulated in the vegetative organs during the vegetative growth and are
subsequently translocated rapidly into the grains after flowering. In maize,
carbohydrate accumulation is less and vegetative growth continues after
silking to some extent. In both crops, however, most starch accumulating
in the grains is the product of photosynthesis during grain-filling.
II. CONTRIBUTION OF LEAVES AT VARIOUS
POSITIONS TO GRAIN YIELD AND
DRY MATTER PRODUCTION
In the previous chapter it was demonstrated that the photosynthetic
products of the leaves during grain-filling are the major components of the
grains. As there are many leaves at various positions on a culm, differential contribution among leaves for grain-filling can be expected. Experiments to demonstrate such a division of function among leaves were
conducted by removing leaves or feeding 14C02 from leaves at various
positions.
The source-sink theory is a handy tool when discussing dry matter production. In the maize plant during grain-filling the leaves and the ears
can be considered as the source and the sink, respectively. Thus, various
treatments of removing leaves or ears were tested to determine the relation
between source and sink.
Effect of Removing Leaves or Ears
Using a Fukko No.8 population, six treatments (Fig. 3) were differentiated by removing the leaf-blade or the ear at silking (TANAKA and FUJITA
(1971)).
Removing all leaves (No.4) resulted in no grain production and a decrease
of the culm weight. Removing leaves above the ear (No.3) caused
a drastic decrease of grain weight. However, removing leaves below the
78
A. TANAKA AND J. YAMAGUCHI
ear (No.2) caused almost no decrease of grain weight. Removing ears
(No.5) caused a significant increase of culm weight and a decrease of total
plant weight. Removing neighboring plants (No.6) did not result in
a remarkable change of weight of any organs.
Removing all leaves (No.4) decreased nitrogen content and increased
200
No.2
No.3
No.4
No.5
No.6
No. I
Control.
No. 2
The leaves at or above the lsi ear were kept
intact and the leaf -blades of the lower leaves
were removed.
The leaves below the 1st ear were kept intact
and the leaf - blades of the upper leaves were
removed.
No.3
No.4
All leaf-blades were removed.
No.5
The ears were removed.
No. 6
The plants in the rows at the both sides of
the test row were removed.
Fig. 3.
Effect of removing leaves or ears on weight of
various organs at harvest (Fukko No.8, 1968)
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
79
culm sugar content (Table 2). Removing ears (No.5) caused a remarkable
incease of sugar content of the leaf-blades and the culm. Also, it resulted
in earlier senescence of the leaves.
TABLE
2.
Effect of removing leaves or ears on sugar
and nitrogen content of the leaf-blades and
the culm* (Fukko No.8, 1968)
Nitrogen (%)
Sugar (%)
Treatment**
Leaf-blades
I
Culm
Leaf-blades
I
Culm
No.1
1.2
5.6
4.1S
No.2
2.4
7.S
2.24
1.S3
l.4S
No.3
1.6
4.4
2.09
1.39
No.4
-
ll.S
-
LOS
No.5
5.0
16.4
2.32
1.49
No.6
1.6
4.9
4.00
1.43
* Including the leaf·sheath.
** See Fig. 3.
Another experiment usmg a Fukko No. 8 population included nine
treatments (Fig. 4) differentiated at silking.
With a decrease of leaf area (No.2- No.5), grain weight and total
plant weight decreased. Removing lower leaves (No.2) caused only a small
decrease of grain weight. Interception of pollination (No.6) resulted in no
grain production, a decrease of total plant weight and an increase of the
weight of vegetative organs. Removing the first ear (No. 7 and No.8)
caused a decrease of total plant weight, an increase of the weight of the
leaf-and-culm and a slight increase of the weight of the second ear when
it was kept intact. Removing the second ear (No.9) caused almost no
change.
Decreasing leaf area by removing the leaves (No.2 - No.5) caused an
increase of the rate of dry matter production per unit leaf area during
grain-filling (Table 3). Removing the first ear (No. 7 and No.8) or the
interception of pollination (No.6) caused a decrease of the rate of dry
matter production per unit leaf area and also caused an increase of sugar
content of vegetative organs, especially in the sheath-and-culm.
Translocation of Photosynthetic Products
D403 x D405 was water cultured with a standard culture soltution.
80
A. TANAKA AND J. YAMAGUCHI
15
10
~
~
V)
~
~
....,
-<::
.~
~
5
No. ,
No.2
No.3
No.4
No.5
No.6
No.7
No. a
No.9
Control.
The lower leaves· were removed.
The lower and the middle leaveS' were removed.
The lower leoves and 72 areo at the tip of the
middle and the upper leaves were removed.
The lower leaves and % area at the tip of tlie
middle and the upper leaves were removed.
Pollination intercepted by buging the ears.
The ears were removed.
The 1st ear was removed.
The 2nd ear Was removed.
* Two
leaves at and just above the 1st ear were designated the middle leaves.
The lower and the upper leayes designate the leaves at lower or upper
positions of the middle leaves, respectively.
Fig. 4.
Effect of removing leaves or ears on weight of
various organs at harvest (Fukko No.8, 1969)
At the beginning of silking, 14C02 was fed to the leaves at three different
positions: two positions above the first ear (the twelfth leaf), the position
of the first ear (the tenth leaf), and two positions below the first ear (the
eighth leaf). Distribution of 14C among the organs 24 hours after the 14C
feeding was traced (TANAKA and FUJITA (1971)). At this stage the upper
leaves and the cob-and-husks, especially those of the second ear, were still
growing vigorously.
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
TABLE
3.
Effect of removing leaves or ears on rate
of dry matter production per unit leaf area
(DMP Rate) and sugar content of the leafblades and the culm* (Fukko No.8, 1969)
Sugar (%)
DMP Rate***
(g·m- 2 ·day-l)
Leaf-blades
No.1
4.77
3.96
2.7
No.2
5.11
17.6
Treatment**
I
Culm
No.3
5.52
No.4
5.34
No.5
5.51
No.6
2.95
1.70
No.7
1.54
6.25
9.8
No.8
3.28
1.98
6.3
No.9
4.67
2.7
* Including the leaf-sheath.
** See Fig. 4.
*** DM PRate = Dry matter production during grain-filling/leaf area at silking/
days from silking to harvest.
'tOt fed from
-=Th"--e---:"12-=-t'--:h---"'-le-a-:r--t1
1-1
,.....--::Th""e--:IO::CtC:h -:Ie-a"--{:--i
-Th-e-B-t-h-I-e-a-f-
l
t-I
Upper" lenves
14C02 fed leaf
Lower" leaves
Upper culm
Lower culm
1st ear
2nd ear
Roots
40
60
40
60
0
20
40
60
Percentage of 14e distributed in each organ on the bases
of total amount of 14e in the plont
Fig. 5.
Distribution of 14C assimilated from the leaves at various
positions (D403 X D405, water cultured)
* "Upper" or "lower" indicate relative to the 14C fed leaf.
80
81
82
A. TANAKA AND
J. YAMAGUCHI
The amount of 14C remaining in the 14C fed leaf was small in all cases
(Fig. 5). The 14C fed to the twelfth leaf was distributed uniformly in the
plant, except in the lower leaves. More 14C was detected in the first ear
than the second ear and in the leaves and the culm above the fed leaf than
below it. Most of the l4C introduced from the tenth leaf was detected in
the second ear and in the culm below the fed leaf. The 14C fed to the
eighth leaf was recovered mostly in the culm below the fed leaf.
Another 14C02 feeding experiment was conducted by using plants in
selected plots of the experiment described in Fig. 4. l4C02 was fed to the
leaf immediately above the first ear of the plants in treatments No.1,
No.2, No.6, No.7 and No.8. In No.3, the lowermost remaining leaf
was chosen to feed 14C02. Distribution of l4C was determined 20 days after
the 14C feeding.
In the control (No.1), most l4C was found in the first ear and only
two percent remained in the HC fed leaf (Table 4). With the removal of
the leaves (No. 2 and No.3), a distribution pattern similar to the control was
TABLE
4.
Effect of removing leaves or ears on l4C* distribution among organs (percentage of total amount
of l4C remaining in the plant) (Fukko No.8, 1969)
Treatment**
No.1
14C fed leaf
Leaves
Culm
Ear
2.3
No.2
2.3
No.3
4.6
No.6
No.7
No.8
12.4
20.9
31.1
Upper***
2.8
0.7
0.2
0.3
2.0
0.6
Lower***
0.4
0.6
0.3
0.5
0.9
2.1
Upper
2.5
3.5
1.0
6.0
11.2
6.0
Middle
1.2
2.4
0.7
6.4
7.9
4.0
Lower
2.0
10.0
1.5
49.7
57.0
47.9
1st
88.7
79.6
91.6
1.9
-
-
2nd
0.1
0.9
0.1
22.8
-
8.3
Percentage of 14C
released from
plant****
I
38
33
38
45
52
53
* 14C02 was fed to the leaf one position above the 1st ear.
** See Fig. 4.
*** "Upper" or "lower" indicate the position relative to the 14C0 2 fed leaf.
**** In all treatments the amount assimilated was almost the same, about 13x
107 cpm (a). From the data of cpm/mg and weight of each organ the total
amount of 14C remaining in the plant (b) was worked out: Percentage
released = (a - b )/a X 100.
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
83
observed. With removal 'of the lower leaves (No.2), however, HC was
distributed more in the lower culm. With removal of the ears (No.7 and
No.8) or the interception of pollination (No.6), more HC remained in the
HC fed leaf, most of the HC translocated from the fed leaf was detected in
the lower culm. Some was also found in the second ear when it was kept
intact.
The percentage of 14C released as CO2 by respiration from the plant
during the 20-day period after 14COz feeding on the basis of the amount
of 14C assimilated at the time of feeding was less than 40 percent with the
control or with the removal of the leaves. The percentage was, however,
higher when the development of the kernels was interrupted.
Discussions
Many reports indicate that the more leaves removed and the earlier,
the less the grain yield from the maize plant (CORNELIUS, RUSSELL and
WOOLEY (1961), MACK (1965)). Similar results were obtained in the experiments described above. This provides further evidence of the importance
of photosynthesis after silking for grain production.
However, removing leaves removes not only their contribution to photosynthesis, but also the nutrients they contain. For this reason, shortage
of some nutrients, especially of nitrogen, might become one of the limiting
factors to kernel development.
Removing all leaves at the beginning of silking resulted in no grain
yield. In this case, increased sugar content in the culm was observed.
This may indicate that with such treatments, failure of fertilization at the
time of flowering rather than shortage of carbohydrates during grain-filling
is the cause of no grain production.
Removing leaves above the ear causes a remarkable decrease of grain
production. Removing leaves below the ear causes only a slight decrease
of the grain yield. Similar results have been reported by several workers
(HOYT and BRADFIELD (1962)). This indicates that the upper leaves play
the most important role in grain-filling and that the contribution to the
grain from the lower leaves is limited.
The results of the experiment with 14COZ fed to the leaves at different
positions on the culm demonstrate that the upper leaves contribute more
to the grains than the lower leaves. The results indicate a preferential
translocation of photosynthetic products from the upper leaves to the grains
and from the lower leaves to the lower culm. This was demonstrated by
PALMER (1969). According to him, the photosynthetic products of the
leaves above the ear trans locate to the grains efficiently and translocation
84
A. TANAKA AND J. YAMAGUCHI
of photosynthetic products from the leaves below the ear to the grains
decreases progressively towards the base of the plant. A similar division
of function among leaves has also been observed in the rice plant (TANAKA
(1961)). In rice, the upper three leaves on a culm send their photosynthetic
products to the grains of the panicle on the culm and the lower leaves
send theirs to the culm or the roots. One important difference is that the
major flow of photosynthetic products to the grains is downward in the
maize plant and upward in the rice plant.
Another possible explanation for the small contribution from the lower
leaves to the grains is that under field conditions the lower leaves are shaded
(HOYT and BRADFIELD (1962)).
For these reasons the dry weight increase of the grains in a crop of
maize depends mostly on the photosynthesis of the leaves above the ear.
Only a limited contribution comes from the lower leaves.
Under favorable conditions, translocation of photosynthetic products
from the leaves is rapid and efficient in the maize plant. Only a small
fraction of the photosynthetic products of a leaf remains in the leaf for
more than 24 hours. The efficient translocation is a characteristic of the
maize plant (EASTIN (1970)). The efficiency is lower in the rice plant
(TANAKA (1961)).
A partial removal of the upper leaves increases the rate of dry matter
production per unit leaf area of the remaining leaves. Such an increased
photosynthetic activity by partial defoliation was reported by KIESSELBACH
(1948). Since the developing kernels are demanding photosynthetic products
from the leaves, a partial removal of leaves increases the demand on the
remaining leaves and the photosynthetic efficiency of these leaves increases.
Similarly, it has been shown that in the maize plant the availability
of storage sites affects production and movement of carbohydrates (Moss
(1962)). Thus, removing the ear or pollination interception causes a decrease
of the rate of dry matter production per unit leaf area. It appears that
if the demand of the developing kernels is interrupted, photosynthesis
by the leaves is adversely affected.
It has also been demonstrated that the growth rate of the kernels
is positively correlated with temperature during grain-filling (RAGLAND,
HATFIELD and BENOIT (1965)). Consequently, an increase of temperature
accelerates demand of the developing kernels and this affects the rate of
photosynthesis by the leaves.
These phenomena can be explained in terms of sources and sinks for
the products of photosynthesis where the leaves are the source and the
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
85
kernels are the sink.
Removing the kernels decreases sink SIze and increases sugar accumulation in the vegetative organs. This type of accumulation of sugars in
the culm, especially that of sucrose, has been reported by several workers
(VERDUIN and LOOMIS (1944), VAN REEN and SINGLETON (1952)). The
culm and the cob act as an additional sink to some extent by accumulating
sucrose when the major sink, the kernels, is missing.
Accumulation of sugars in these organs increases respiration. In normal
plants, about 40 percent of the photosynthetic products are consumed by
respiration. With plants in which sugars have accumulated because development of the kernels has been prevented, more than 50 percent is consumed.
Accumulation of sugars in the leaf-blades results in a decrease in the
photosynthetic rate. Also, it accelerates the senescence of leaves (ALLISON
and WEINMANN (1970)).
A decrease in the rate of photosynthesis, an increase in the rate of
respiration and earlier senescence of the leaves result in reduced total dry
matter production.
In the rice plant, removing the ears causes an accumulation of starch
in the culm and in the leaf-sheath and eventually, development of new
tillers. This was not observed in maize plants.
Removing adjacent plants at silking from a maize population spaced
50 cm x 50 cm which had a leaf area index (LAI) of about four did not
cause a significant increase of the dry matter production of the remaining
plants. This indicates that the solar energy available to individual plant
was not the limiting factor for the dry matter production after silking, at
least under the given environmental condition.
The evidence from these experiments and from others to which reference has been made, supports the view that the grains are formed from the
products of photosynthesis in the leaves above the ear during grain-filling.
Photosynthetic activity of these upper leaves is, however, controlled by the
activity of the kernels as the sink.
III. DRY MATTER PRODUCTION, PHOTOSYNTHESIS AND RESPIRATION
Dry matter production is the balance between photosynthesis and respiration. The rates of these physiological processes differ among organs,
ages, cultural conditions, etc. Discussions in the previous chapter revealed
that the situation of the relation between source and sink interacts with
the rates of photosynthesis and respiration.
A. TANAKA AND J. YAMAGUCHI
86
Various data on photosynthesis and respiration were collected for
a better understanding of dry matter production.
Photosynthetic Rate
Apparent rate of photosynthesis of each organ of a Fukko No. 8
population was determined during grain-filling (TANAKA, YAMAGUCHI and
IMAI (1971)). In full sunlight the apparent rate of photosynthesis was large
in the leaf-blade, small in the sheath-and-culm and negative in the ear (5.08,
0.16 and - 0.55 g CO2, m -2field· hr-l, respectively). The rate of photosynthesis of the ear at the milky stage was about half its respiratory rate.
This indicates that maize photosynthesis depends mostly on the leafblade and only slightly on the sheath-and-culm.
By using the plants in the same population, the rate of photosynthesis
per unit leaf area (po) of leaves at various positions on the culm was
measured at successive growth stages.
The po of a lower leaf (the sixth leaf) was about 60 mg CO2, dm -2. hr- 1
at full expansion and decreased with age (Fig. 6). The po of a middle leaf
Photosynthesis
,
~eaf
~f
'0
.~~\
• ( · , ' 6 t h leaf
.~~.~:
.
.--------
.
7th/ea~.
Respiration
~
~
th/eaf
lIihleaf
~.
~~
2
~~
.----.
16th/eaf
7thl;a
~
.~----------:
O~~~:---~~,---~~--~~~---~~'~~---
July /6
Fig. 6.
July 31
Aug /5
Aug 30
Sept /4
Fluctuation of rates of photosynthesis and
respiration of the leaves at various positions
during growth (Fukko No.8, 1969)
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
87
(the eleventh leaf) was as high as 80 mg CO2 • dm -2. hr- 1 at full expansion,
decreased slowly with age, increased again during the initial grain-filling
phase, reached a maximum at the beginning of the active grain-filling phase
and then decreased again. The po of the top leaf (the sixteenth leaf) was
rather low when it completed expansion, started to increase from about
10 days after silking, reached a maximum of about 60 mg CO2 ·dm- 2 ·hr- 1
at the beginning of the active grain-filling phase and then decreased.
At a given growth stage, the po was higher in the leaves which had
just completed their expansion than in younger or older leaves (Table 5).
Leaves with a high po contained less sugar than those with a low po.
These data show that the po of a leaf is low when it is expanding,
reaches a maximum when it has completed expansion and then decreases
with age. Translocation of photosynthetic products is more active from
leaves which have just completed expansion and the active photosynthesis
of these leaves appears to be associated with an active translocation. The
rate of translocation decreases, sugar content increases and the po decreases
with age. The low content of
nitrogen and phosphorus of old
80
leaves (Table 1) may also be
~;;
5. Photosynthetic rate (po)*
and sugar content of leaves at
various positions on the culm
at silking (Fukko No.8, 1969)
TABLE
Leaf
position**
po
(mg CO 2 •
dm- 2 ·hr- 1 )
Sugar
16
36
2.09
15
44
1.96
14
43
2.07
13
72
1.10
12
69
1.24
11
64
1.72
10
59
1.81
9
45
2.01
/
(%)
8
44
2.74
7
37
2.71
6
20
5.30
Light
Fig. 7.
* Measured at 80 klux.
** Counted from the bottom.
40
00
intensity
(klux)
80
Photoresponse curves of photosynthetic rate of the 11th leaf at various
growth stages (Fukko No.8, 1969)
A. TANAKA AND J. YAMAGUCHI
88
related to the low po values of these leaves.
Leaves which have recently expanded had a high rate of photosynthesis
and responded to high light intensity. For example, the po of the eleventh
leaf did not show photosaturation up to 80 klux. However, the po and
the response of the po to light intensity decreased with age (Fig. 7).
The po is also affected by the nutritional status of leaves. D403 x D405
was grown in water culture with graded levels of nitrogen, phosphorus and
potassium in the culture solution. The po of the leaves and the content of
these three elements in the leaves at different positions were measured at
successive stages of growth (TANAKA and HARA (1970, 1971a)).
~
60
::"
~
i
1
"
~
'§ 40
~
::
Ji
.,~
20
0
a
~o
0
0
0
0
O_.Q
0
0
0
0
•
o •
••
...• ."
0"
rP
o·
0
•
"
.'lo
ct
00
•2•
"
'.I:'
"
~
0
....
0
0
0
o.
IJ
0
0
0
0
000
0 - 0 0-00
0
00
"0
t··,
o
.---
0
0
~
'-
:g
a
o
I·
3
NO/O
4
5
0
0.2
0.3
04 0.5
0
2
P%
3
4
K%
o Element deficient ar normal leaves.
o Leaves from plants grown with culture solutions at higher concentrations
than ISO ppm N, SO ppm P or ISO ppm K.
(Open and solid symbols represent young and old
Fig. 8.
le(Jve~,
respectively).
Relation between nutrient content and photosynthetic
rate (D403X D405, water cultured)
There was an association between po and nutrient content (Fig. 8). In
newly expanded leaves, the greater the content of N, P or K, the larger
was the po. However, the increase in po ceased when the content of N, P
and K reached 4 percent, 0.4 percent and l.5 percent, respectively. The
po of old leaves or of leaves from plants grown with excess nitrogen or
phosphorus was lower than the expected value from their nutrient content.
Response of the po to light intensity is also affected by the nutrient
status of leaves. Leaves deficient in nutrients have a low po and also a low
photosaturation point (Fig. 9).
The first ear of a Fukko No.8 plant was removed at silking. The po
of the leaf immediately above the ear of a control plant and the po of
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
cO
50 ppm N, 12 ppm P,
50ppm k
•
:::---
,,'~
~
~ 40
~
'-
..:!l
~
.~
400ppm N.
~
~
·--------------------------~O~p.=p:m~K~'·
ct:
------- ---------------------~a~.3~p=pm:roP·
~
40
20
80
60
Light intensity (klux)
Fig. 9.
Photoresponse curves of photosynthetic rate of
the 15th leaf affected by nitrogen, phosphorus
and potassium status (D403xD405, water cultured)
(Letters in the figure indicate the concentration of
elements in culture solution)
I
~
1
M~~
x_ _ _ _
~
~~
\
~x
~ 40
Q
~o_--
~
~
~
2
~
____-<o
x
~
Control
x Ear removed
20
0
:s~
x
.§
it'"
-="::=::::.:-~J~;;;;~~~~=====::~~~::::::~-"=~::~~~~~~-~~~~~~-:~~~~~~~====~
00
10
20
30
40
Days after silking
Fig. 10.
Effect of removing ear on rates of photosynthesis
and respiration of the leaf at one position above
the ear (Fukko No.8)
4
2
89
A. TANAKA AND J. YAMAGUCHI
90
the corresponding leaf of a plant from which the ear had been removed
were measured for 50 days from the removal of the ear (TANAKA and
FUJITA (1971)). The po of the plant without an ear was apparently lower
than that of the control plant (Fig. 10). This indicates the importance of
sink for maintenance of a high po.
The diurnal fluctuation in the rate of photosynthesis of the Fukko
No.8 population which was used to collect the data in Fig. 7 was traced
at three growth stages by the methods described elsewhere (TANAKA,
KA W ANO and YAMAGUCHI (1966)) and the data are plotted against the
corresponding light intensities for each measurement (Fig. 11) (TANAKA,
YAMAGUCHI and IMAI (1971)).
6
~r--------OZ~O---------4~O~-------6~O
Horizontal light intensity (klux)
Fig. 11.
Photoresponse curves of photosynthetic rate of a population at various growth stages (Fukko No.8, 1969)
On August 11, the rate of photosynthesis was high and its response to
light intensity was high, also. The LAI on August 11 and on August 22
was about 4. However, the rate of photosynthesis and the response of this
rate to change in light intensity decreased from August 11 to August 22.
There was a further decrease in the response to light intensity from August
22 to September 12, although the rate at lower light intensities was somewhat
higher on September 12 than on August 22. These changes can be well
interpreted on the basis of changes of the po of each leaf which were
illustrated in Fig. 7.
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
91
Respiratory Rate
The respiratory rate per unit leaf area decreased with age (Fig. 6)
(TANAKA, YAMAGUCHI and HARA (1971a)). However, there was an increase
during the active grain-filling phase in the middle and the upper leaves.
At a given growth stage, the respiratory rate was high in very young leaves
and low in old leaves which were dying. With these exceptions, differences
in the rates of respiration of the leaves were small.
Data from the water-culture experiment with graded levels of nutrients
indicate a positive correlation between the respiratory rate and the po
(Fig. 12). The correlation is not lineal. At low po, the respiration-photosynthesis ratio was higher than at high po.
60
0
o
00
00
0
0
o
~
-":
\--0
~40
~
•
0
'-
•
o
o.
o
Young leaves
• Old leaves
/'
~~--------~---------2~--------~3~----­
Fig. 12.
Respiratory rate (mg COz · dm-z. hr- I )
Relation between respiratory rate and photosynthetic rate
This relationship between po and respiratory rate does not always hold
true. For example, the ear removing experiment cited in Fig. 10 demonstrated that removing the ear increased the respiratory rate and decreased po.
The respiratory rate per unit weight of the leaf-blades, the sheath-andculm and the ear was measured at successive stages of growth. It was
higher in the leaf-blades than in the sheath-and-culm (Table 6). At silking,
the respiratory rate of the tassel and the ear was higher than that of the
leaf-blades. The rate of each organ decreased with age.
During the early part of the vegetative phase, the respiration of the
leaf-blades was greater than that of the sheath-and-culm. However, at
92
A. TANAKA AND J. YAMAGUCHI
TABLE
6.
Respiratory rate of various organs at various
stages of growth (Fukko No.8, 1969)
Growth stage
I
Ear-initiation
Tasseling
Organ
Respiratory rate
(mg CO 2·g-l.hr- 1)
Leaf-blades
65
4.25
Sheath-and-culm
50
3.99
Leaf-blades
150
1.96
Sheath-and-culm
250
1.40
31
2.30
Days after silking 3
15
Dry weight
(g·m -2field)
Tassel
25
20
2.03
20
1.00
0.84
Days after silking 3
52
2.38
15
200
2.03
25
37
25
37
47
Ear
390
1.55
655
0.90
835
0.46
tasseling the dry weight of the sheath-and-culm was greater than that of
the leaf-blades and its respiration also was greater. The tassel respiration
was about 5 percent of the respiration of the whole plant at silking and
decreased rapidly. The proportion of the respiration of the whole plant
that was accounted for by the ears increased after silking, reached 60 percent by the end of the initial grain-filling phase, was maintained at this
level for more than 20 days and then decreased to about 40 percent at
maturity.
Dry Matter Production Related to Photosynthesis and Respiration
Growth efficiency (GE) was defined here as the ratio of the amount of
dry matter produced to the amount of materials used for the production
(TANAKA and YAMAGUCHI (1968)).
Seeds of Wisconsin Hyb. Corn No. 95 were germinated in the dark at
different temperatures (TANAKA and YAMAGUCHI (1969)). The higher the
temperature, the higher was the growth rate of seedlings (Fig. 13). The
GE of seedlings, calculated as the ratio of the seedling weight increase to
the seed weight decrease, was maintained at about 70 percent regardless of
temperature between 15°C and 35°C until the materials in the seeds were
exhausted.
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
93
The GE decreased abruptly when
the reserved materials for germination in
-'"
~100
the seeds were exhausted. After this
~
growth stage, the weight of old leaves
..,~""
and roots starts to decrease. The GE
~ 50
should then be expressed as the ratio
":::.~'"
of the increased weight of new organs
~
to the deceased weight of old organs.
00
200
300
400
Hours ofter sowing
The GE calculated on this basis was
80
about 50 percent for a longer period.
~
This demonstrates that the GE is
'" 1
low when reutilization of materials in old
organs is occurring.
Using a Fukko No. 8 population,
~ 0
0:
<:!l
the plant weight and the rate of dark
respiration were measured regularly dur-40
ing
growth (Y AMAGUCHI, HARA, and
Fig. 13. Effect of temperature on
weight of seedlings and
TANAKA (1970)). The relative growth
growth efficiency at sucrate (RGR = AW/(W . At), where W is the
cessive stages of germiplant weight and AW is the dry matter
nation
production during a period of At), and
the rate of respiration per unit plant weight (R) were computed from the
data obtained. The GE was calculated by the formula, GE=RGR/(RGR +
R). The rate of respiration is assumed to be the same in the light and in
the dark.
The RGR and the R in80r-------------~~----,
creased for 40 days after sowing
! 60
and then decreased gradually until
maturity (Fig. 14). Low values at
f"-.... RGR
' \ 200
early growth stages were probably
due to low spring temperatures.
The GE was kept between 60
percent and 65 percent until silking, decreased gradually for some
Days after sowing
time and then decreased more
Fig. 14. Fluctuation of respiratory rate
rapidly to about 40 percent at
(R), relative growth rate (RGR)
and growth efficiency (GE) of
maturity.
a population during growth
The rate of respiration and
(Fukko No.8, 1968)
the dry weight of the ears were
~
, #f
~E
A. TANAKA AND J. YAMAGUCHI
94
measured at successive stages of grain-filling. Then the GE of the ear at
successive stages of growth was computed (TANAKA, YAMAGUCHI, and
HARA (1971)). The GE of the ear was maintained between 70 percent and
75 percent throughout the grain-filling phase.
Photosynthesis and Respiration at Stratified Strata of Population
The dry weight, the rate of photosynthesis at a full sunlight and
the rate of respiration in the dark of 40 cm strata within the canopy of
a population of a Fukko No. 8 were measured at the milky stage (TANAKA,
YAMAGUCHI and HARA (1971a)).
Respiratory role
(g C~-m-2 field-hi'per stratum)
LTR (%)
300 'i------"ir-------'-"i'-
2
Leaf area (m'-m-'field per stratum)
Fig. 15.
Dry weight (g-m-'field per stratum)
Photosynthetic rate (g COz-ni'field-hi'per stratum)
Leaf area, light transmission ratio (LTR), dry weight,
photosynthetic rate and respiratory rate at various strata
of a population during grain-filling (Fukko No_ 8, 1969)
The light transmission ratio decreased from the top to the bottom of
the canopy (Fig. 15). The decrerse was significant at the upper and the
middle strata. A large proportion of the leaf area was situated in the
middle strata where the ears were formed. There was very little leaf area in
the lower strata but a large fraction of the culm weight is at this level.
With the exception of the top stratum where the tassels were located,
the rate of photosynthesis was high in the upper strata of the canopy.
The rate of respiration in the 120-80 cm stratum was the highest because
of the active respiration of the ears.
From these data, the balance between photosynthesis and respiration
during a one day cycle were estimated for each stratum. For estimating
the amount of photosynthesis, the rate of photosynthesis of each stratum
at full sunlight, the light transmission ratio at various height, the light
response curves of the photosynthetic rate of the population presented in
Fig. 11 and a typical :fluctuation curve of solar radiation during a day in
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
95
this season were used. The rate of respiration was assumed to be kept
constant at the rate in the dark.
TABLE
7.
Stratum*
(em)
I Photosynthesis I
(a~)b) (%)
(a)
Respiration
(b)
246-200
1.21
0.59
0.62
51
200-160
13.51
1.48
12.03
89
160-120
10.64
3.17
7.47
70
120- 80
4.81
4.69
0.12
80- 40
1.73
0.63
1.10
64
40- 0
0.36
0.18
0.18
50
32.26
10.74
21.52
67
Total
*
Estimated amount of photosynthesis and respiration
at each stratum of a crop canopy during grain-filling
(g CH2 0'm- 2 ·day-I) (Fukko No.8, 1969)
(a-b)
I
2.5
Height from the ground.
The estimates presented in Table 7 indicate that photosynthesis was
largest in the 200-160 cm stratum and respiration was largest in the
120-80 cm stratum. The balance between photosynthesis and respiration
was largest in the 200-160 cm stratum. The balance was about 90 percent
of the total photosynthesis in the 200-160 em stratum, about 3 percent in
the 120-80 cm stratum and 50-60 percent in the 80-0 em stratum.
The method of estimation used here is based on various assamptions
and subjects to criticisms. However, it indicates fairly clearly that the 200160 cm stratum is the site of production and the 120-80 cm stratum where
the ears are located is the site of consumption and storage.
Discussions
It was reported that there is no photo saturation point in the photosynthesis of maize populations (BAKER and MUSGRAVE (1964)). In rice populations there is a photo saturation point when LAI is small, but it does not
exist when the LAI is large (TAKEDA (1961), MURATA (1961)). However,
there is a photosaturation point, even in maize populations with a reasonably
large LAI, at later stages of grain-filling when all the leaves are old. The
changes in the rate of photosynthesis of a population can be explained by
the variation in the po.
It has been pointed out that the po is apparently higher in the maize
plant than in other crops (HESKETH (1963), WAGGONER, Moss and HESKETH
96
A. TANAKA AND J. YAMAGUCHI
(1963)), including rice (MURATA (1961), TANAKA, KAWANO and YAMAGUCHI
(1966)). The po of maize increases with an increase of light intensity and
does not show photo saturation even at full sunlight, whereas rice is light
saturated at about 40 klux. High po is an extremely important characteristic
of maize for it is the basis of high yielding ability.
The po increases with an increase of nutrient content in the leaf up to
a certain value. The critical percentages in the leaves of maize appear to
be approximately the same as those of rice (TANAKA (1961)). Old leaves,
however, generally show a lower po, even though they have an adequate
nutrient content. It has been noted that the photosynthesis of a leaf
declines with age due to translocation of nutrients from the leaf, especially
potassium (Moss and PEASLEE (1965)). In the observations reported in
this paper, the po decreased without any significant decrease of potassium
content. The decrease of po with age can not always be considered a simple
nutritional deficiency.
The translocation of photosynthetic products from a leaf is active when
it has just completed its expansion. With age, the translocation becomes
slower because younger leaves become the major source to the growing
point. Under such conditions, sugars accumulate in the old leaves and the
po of these leaves decreases.
Although the po of a healthy, newly expanded leaf is higher and
responds better to high light intensity in the maize plant than in the rice
plant, the po is strongly influenced by age and by nutritional status. It
can be low even in maize under some circumstances.
The po of several leaves at or above the ear, the major source for the
developing kernels, increases when grain-filling is active. This type of
increase has been reported in the flag leaf of the rice plant under certain
conditions (MURATA (1961». By removing the ear, the po of these leaves
decreases. This indicates that these leaves are performing an important
role in grain-filling and the rate of dry matter accumulation in the kernels
influences the po of these leaves.
The GE of germinating maize seedlings is about 70 percent between
15°C and 35°C. This value is slightly higher than that of rice (TANAKA
and YAMAGUCHI (1969)).
During the vegetative growth phase, the GE of maize populations is
kept almost constant between 60 percent and 65 percent. During grainfilling, however, it decreases. A lower GE value during this phase is due to
the respiration of organs other than the ears. Reutilization of substances,
especially nitrogen compounds in the leaves and in the culm for grain-filling
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
97
may be another low GE value factor. The GE of rice is almost the same
as maize during early stages of growth, but is lower during grain-filling
(TANAKA and YAMAGUCHI (1968)).
In maize high night temperatures promote respiration and result in
accelerated photosynthesis in the day time. So, activated respiration caused
by a high temperature can not be considered a negative factor for grain
yield (Moss, MUSGRAVE and LEMON (1961)). On the other hand, in rice
many reports indicate that higher temperatures than a certain limit may
accelerate respiratory loss and result in a decreased grain yield (MURATA
(1964)). The difference may be that in rice a higher proportion of respiration is not directly linked with grain-filling.
Most of the photosynthesis in maize is at the top of canopy (WRIGHT
and LEMON (1966), UCHIJIMA, UDAGA W A, HORIE and KOBAYASHI (1967)).
During grain-filling, the upper strata of the crop where the active leaves
are located are the main producers. Photosynthetic products from the upper
strata are translocated to the middle strata where the ears are located.
Part of the translocated material is respired and the remammg part is
converted to starch in the kernels. In the lower strata, photosynthesis and
respiration are reasonably well balanced.
In rice, respiration and photosynthesis is high in the upper strata
where the panicles and the leaves are located. It is in this layer that most
of the production, consumption and storage occurs. In the lower strata,
where leaves are shaded and the sheath-and-culm are located, there is more
respiration than photosynthesis. There appears to be more respiration in
the lower strata in rice than in maize (TANAKA and YAMAGUCHI (1968)).
However, it should be mentioned that the data for rice was obtained using
varieties with a poor plant type. For improved varieties with good plant
type, the lower stratum does not consume a large amount of the photosynthetic products of the upper stratum (YOSHIDA, COCK and PARAO (1971)).
To summarize, the po of young leaves of maize is larger than that of
rice. However, as a leaf ages the demand on it for photosynthetic products
decreases and this results in a low po even if the leaf maintains a high
potential productivity. The efficiency of respiration in dry matter production
during grain-filling is higher in maize than in rice, Also, the demands of
the lower layers of the crop canopy for respiratory substrates from the upper
layers is smaller in maize than in rice. For these reasons, it seems that
the rate of photosynthesis of the crop during grain-filling is more intimately controlled by the demand of the developing kernels for photosynthetic products in maize than in rice.
98
A. TANAKA AND
J. YAMAGUCHI
IV. VARIETAL TRAITS ASSOCIATED
WITH YIELDING ABILITY
Hybrids generally give higher grain yield than their parental inbreds.
Varietal difference in yielding ability is also obvious. It is needless to
mention that many plant traits are associated with the yielding ability.
With these backgrounds varietal comparisons of various traits were
TABLE
8.
Grain yield, total plant weight and photosynthetic
rate (po) of hybrids and their parents (1968)
Grain yield
(g/plant)
Line
I
Total J?lant
weight
(gjplant)
I
Grain: total
weight ratio
I
po*
(mg CO 2 ,
dm- 2 ·hr- 1)
WF9
17
173
0.10
24.7
OH51 A
70
163
0.43
28.0
OH43
44
113
0.39
17.0
OH45
59
150
0.39
28.4
WF9xOH51 A
217
452
0.48
25.9
OH43x OH45
124
264
0.47
31.3
Ko No. 504**
185
336
0.55
28.1
* Measured on the leaf just above the ear during grain-filling at 55 klux.
** Ko No. 504= [(WF9x OH51 A )x(OH43x OH45)].
TABLE
9.
Hybrids and their parents tested (1969)
Parental inbred
Combination
No.
I
Mark
Hybrid
I
I
Mark
I
Mark
1
W153 R
A
W25
B
WI53 R xW25
2
OH43
C
OH45
D
OH43xOH45
CD
3
W9
E
WM13 R
F
W9xWM13 R
EF
4
W23
G
W28
H
W23xW28
GH
5
C13
C30
J
C13x C30
I J
6
P39
I
K
P51 B
L
Golden Cross Bantam
KL
7
D403
M
D405
N
D403xD405
MN
8
T102
0
T107
P
T102x TI07
OP
9
OH51 A
Q
WF9
R
OH51 A xWF9
QR
10
Ma21547
Cl3
I
Golden Beauty
S I
11
W49
S
U
WH
V
W49xWH
UV
12
A357
W
OH40 B
X
A357X OH40 B
WX
13
N21
Y
N19
Z
N21xN19
YZ
AB
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
made in this chapter to pinpoint the key factor of varietal difference
yielding ability.
99
III
Heterosis and Yielding Ability
Seven lines (or varieties) related to each other as indicated in Table 8
were planted at 60 cm x 60 cm. Heterosis in the grain yield was positive in
the single crosses but was not observed in the double cross. The same
200
EF
o
~
'"
"'-
A8
~
o
IJ
~
~
.....
-<:
100
yz
0
Y
A
• o .E • •
•
F 0
li:
."<:
'"
••
M
°0
400
I
DC
0
o Hybrid
H ••
100
o
R
1200
G
"\;
•
•
""
"-
'%"
~ ~
100
101
o
00
:;::.
~
MN
:.0 ,~
o
oYZ
y
OIJ
I
o
eF
OJ
ez
10
20
30
Plant weight at 70 days after sowing (g per plant)
{
EF
OP
)2'
0
Q; ..i1 olJ At
o
~ 30
w: Uo"°f(~SI
~
.~
o
~
~
EF
0
o
•
•
.N
e8
QR
o
AB
coo
L
400
/(L
GH
~
0:
o
200
§
<l'.300
~
;;:s
• Parent
•
~
~
"-
R
o
Plant weight at harvest
(g per plant)
~
o
coo
L
G
• a
•
B
J
o
0
/(
0
z
/(L
o
GH
loiN
0
.~
{lR
OGH
1
20
eoeo
~
~
~
~
70
·.0
Gxw
~
~
o og
M
00
10
20
30
Plant weight ot 5 doys ofter sowiflg (rng
Fig. 16.
per plont)
Relation among grain weight, plant weight at harvest,
at 70 days and at 5 days after sowing in thirteen hybrids
and their parents (1969) (Letters in figure indicate:Iines
listed in Table 9)
100
A. TANAKA AND J. YAMAGUCHI
trend was observed in total plant weigtht and in the ratio of grain: total
plant weight. Varietal differences in the po were statistically significant.
A positive heterosis in the po was observed in OH43 X OH45 but not in the
other combinations. There was no association between grain yield and po.
In another experiment, 13 FJ hybrids and their parents listed in Table 9
were sown at a wide spacing (TANAKA and HAY AKA W A (1971)). There
was positive heterosis in grain yield and in total plant weight at harvest
(Fig. 16, top). A statistically significant positive correlation between grain
yield and total plant weight at harvest was observed. The ratio of grain:
total plant weight tended to be smaller in the parents.
There were statistically significant positive correlations between plant
weight at harvest and at 70 days after sowing (Fig. 16, middle), and
between plant weight at 70 days after sowing and weight of seedlings
which were germinated in the dark for 5 days at 20°C (Fig. 16, bottom).
TABLE
Combination*
No.
10.
Days from sowing to emergence and
from sowing to silking of hybrids and
their parents (1969)
From sowing to emergence
(days)
Hybrid
I
MPY**
I Difference
From sowing to silking
(days)
Hybrid
I
MPY**
I Difference
1
18
25.5
7.5
81
93.5
12.5
2
22
24.5
2.5
92
99.5
7.5
3
18
22.0
2.0
81
87.5
6.5
4
20
23.0
3.0
85
102.0
17.0
5
21
21.5
0.5
81
80.5
-0.5
6
20
21.5
1.5
92
97.5
5.5
100.5
17.5
7
16
23.0
7.0
83
8***
20
24.5
4.5
-
9
20
26.5
6.5
89
10***
18
21.0
3.0
-
-
-
11***
20
25.5
5.5
-
-
-
12***
19
27.5
8.5
-
-
-
13
19
20.5
1.5
78
86.0
8.0
Average
4.9
-
-
100.5
11.5
9.5
* See Table 9.
** MPY: Mid Parents Value.
*** These combinations were discarded 70 days after sowing because of poor
germination in parents.
==
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
101
W23xW28
There was a close positive
correlation between leaf area and Plant weigilt
Leaf weight
plant weight during growth.
The time from sowing to Po
TI02 x TlOl
emergence and from sowing to
silking was shorter for hybrids Plant weight I
than the mid-parent values by Leaf weight
•
_ _•
5 days and 10 days, respectively Po
(Table 10).
W/53 Rx W25
No significant heterosis was
Plont weight
observed in the seed weight, the Leaf weight • • • • • • • • • • •
embryo weight or in the GE dur~
•.
ing germination.
Three sets of parents and
o
100
200
their hybrids (No.1, No.4, and
Heterosis %*
No.8 in Table 9) were grown in
Fig. 17. Degree of heterosis in plant weight,
standard culture solution. Fifty
leaf weight, and photosynthetic rate
days after sowing, there was
(po)** in three combinations at 50
days after sowing
a significant positive heterosis in
*
Taking the mid-parents value as 100.
plant weight and leaf weight (Fig.
** Average of several measurements
17). The po of hybrids was higher
on the most active leaves.
than that of the mid-parent value.
However, the difference in the po was statistically significant only in W153 R
X W25.
In this set, the po of the hybrid exceeded the higher parent
value. In other sets, however, the po of the hybrids was lower than that
of their higher parents though the difference between the hybrid and its higher
parent was not statistically significant.
. 1• • • • • • • • •
I
..........
Comparison among Varieties
Fifteen commercial varieties listed in Table 11 were planted at the
spacing of 40 cm X 40 cm in 1968, a year of reasonably good weather.
The grain yield ranged from 4.78 to 10.6 tons/ha. Dates of silking ranged
from July 22 to August 17. Ko No. 3 silked latest and its grain yield
was lowest though its total plant weight at harvest was largest. This
demonstrates that an extremely late silking results in a low grain yield.
The plant height ranged from 157 cm to 289 cm. There was no simple
correlation between plant height and grain yield. There was a tendency
for grain yield to increase with total dry matter production. The varietal
difference in the ratio of grain: total plant weight was small, except for Ko
No.3 in which the ratio was small due to late silking. Golden Beauty
A. TANAKA AND J. YAMAGUCHI
102
TABLE
No.
11.
Grain yield and various plant traits
of fifteen varieties (1968)
Total
Kernel
weight Grain: number 1000Date of Plant
total
kernel
2
height LAI
at
weight per m weight
silking
harvest
field
ratio
(g)
(10 3)
(em)
(kg/m2 )
(tons/ha)
Grain
Type* yield
Varieties
1
D403XD405
D
9.58
Aug. 2
233
3.14
1.56
0.54
2.95
325
2
Wis. Hyh.
95
D
8.41
Aug. 4
245
4.39
1.41
0.52
2.78
303
D
6.39
Aug. 5
232
4.49
1.40
0.41
2.47
259
235
3.19
1.37
0.52
2.75
293
281
"
100
4
"
105
D
8.07
Aug. 5
5
"
110
D
10.64
Aug. 6
219
4.70
1.82
0.52
3.79
"
115
D
9.29
Aug. 11
236
3.99
1.64
0.50
3.59
259
120
D
8.93
Aug. 11
248
4.57
1.65
0.48
3.66
244
D
9.15
Aug. 12
289
5.62
1.89
0.43
3.44
266
3
6
7
8
"
Giants
9
Ko No.3
DF
4.78
Aug. 17
269
5.34
2.08
0.20
2.26
212
10
Ko No.4
F
7.52
J u I. 29
226
5.14
1.29
0.52
2.30
327
11
Ko No.6
DF
9.89
Aug. 4
289
6.34
1.73
0.51
2.71
365
12
Sakashita
F
6.31
3.72
1.08
0.53
1.76
359
Fukko No.4
D
8.66
J u I. 31
J u I. 29
235
13
235
3.62
1.34
0.57
2.62
330
14
Fukko No.6
D
10.37
Aug. 4
229
4.36
1.63
0.56
3.40
305
15
Golden Beauty
S
6.43
J u I. 22
157
4.08
0.91
0.63
2.08
309
* D: Dent, F: Flint, S: Sweet, DF: DentxFlint.
and Giants had a high and a low ratio of grain: total plant weight, respectively. These were the shortest and the tallest varieties.
There was a positive correlation between number of kernels per unit
field area and grain yield, but no correlation between WOO-kernel weight
and grain yield. However, the grain yield of Ko No.3 was low because
of a low lOOO-kernel weight due to a short grain-filling period.
In 1969, 15 leading commercial varieties listed in Table 12 were compared (TANAKA and MORISADA (1971)). The weather was less favorable
than normal. Two spacings, 60 cm x 60 cm and 30 cm X 30 cm, were used.
In August, some plants in the 30 cm x 30 cm spacing lodged because of
strong wind. All plants at this spacing were supported with strings.
The grain yield ranged from 2.61 to 4.69 tons/ha at 60 cm X 60 cm and
from 2.52 to 7.55 tons/ha at 30 cm x 30 cm (Table 12). The grain yield at
30 cm x 30 cm was higher than at 60 cm X 60 cm. However, there was
a varietal difference in response to spacing. In Fukko No.8, D403 x D405
and Ko No.8, the response to close spacing and the grain yield at 30 cm
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
TABLE
No.
12.
Grain yield, date of silking and photosynthetic
rate (po) of fifteen commercial varieties (1969)
Variety
Type*
Grain yield
(tons/ha)
50 em 130em
x60cm x30cm
Date of
silking
po** (mg CO2 '
dm- 2 ·hr- 1)
60em 130em
x60cm x30cm
1
Ko No.8
D
4.26
5.99
Aug. 19
41
33
2
Ko No. 504
D
3.01
5.34
Aug. 18
48
39
3
Long Fellow
F
2.90
3.69
Aug. 11
43
45
4
D403xD405
D
3.71
6.59
Aug. 13
57
32
5
Giants
D
2.89
3.43
Aug. 22
49
34
6
Ko No.4
F
3.81
4.56
Aug.
6
38
30
7
Ko No.6
DF
3.78
5.20
Aug. 16
44
37
37
8
Sakashita
F
2.61
2.89
Aug.
4
37
9
Fukko No.4
D
4.69
5.25
Aug.
4
38
30
10
Fukko No.8
D
4.53
7.55
Aug. 15
42
34
11
Golden Beauty
S
J u I. 29
47
41
12
Golden Cross Bantam
S
3.52
2.95
Aug. 15
41
29
13
Onowa
F
3.87
2.52
Aug. 13
52
27
14
Wis. Hyb. 100
D
3.86
5.42
Aug. 15
57
50
no
D
4.06
5.11
Aug. 14
49
42
15
"
103
-***
-***
* D: Dent, F: Flint, S: Sweet, DF: Dent X Flint.
** Average of duplicate measurements on the leaf just above the 1st ear at
silking at 50 klux.
*** Data are missing because of rats attack.
x 30 cm were greater than for other varieties. Onowa and Golden Cross
Bantam showed a negative response to a decrease of spacing and the grain
yield at 30 cm x 30 cm was low.
No correlation between grain yield and plant height was observed.
There were, however, no extremely short or extremely tall varieties among
high yielding varieties. At close spacings, the plants were more susceptible
to lodging because the culms were taller and thinner. There was no
correlation between grain yield and tiller number.
Grain yield was positively correlated with number of ears per unit field
area at 30 cm x 30 cm, but this tendency did not exist at 60 cm x 60 cm
(Fig. 18, top). At 30 cm x 30 cm, the number of ears was less than the
number of plants. This indicates that the number of ears at this spacing
was determined by the barren plant percentage. A larger number of kernels
per ear associated with a higher grain yield at 30 cm x 30 cm, except in
Giants which had an extremely low 1000-kernel weight due to late silking
104
A. TANAKA AND J. YAMAGUCHI
8
/0
8
•
60cm x 60cm
o 30cm x 30cm
0
10
o
4
o
I
o
6
~ ~7i
15
09
10
0
o
'0 e6
4 6 0 015
8
•
o •
8 13
4
6
8
Number of ears per mZ field
o 60cm x 60cm
• 30cm x 30cm
••
I
6
•9
8.-
12
~
o
0
7
•
4
14
•2 • /5
•
6
o
'6
g
I
o
4
7
o
o
IS
0/4
o
0
2
3
o
08
o
10
o
13
[,
e5
05
TO
"0
6
12
12.~. 02
/3
2
3.°0° 13
•
'6
0
5
o
4
6
8
10
Dry matter prodlJction ofter silking (tons/hoY
Fig. 20. Relation between dry matter
production after silking and
grain yield in fifteen varieties
(1969)
(Numbers in figure indicate
varieties listed in Table 12)
13
2
200
300
500
400
600
/0
Number of kernels per ear
•
9
Fig. 18. Grain yield as related to number of
ears per unit field area and with
number of kernels per ear in fifteen
varieties (1969) (Numbers in figure
indicate varieties listed in Table 12)
't
96 15 5
o 0'
/Z
\
\
300
.~
\
I
I
'pl3 \
\06 \I
I
I
I
I
I
I
\ 30
t 80
I
0
\
\
09 \
\
I
\
0
\
\
\
'0
8
\
\
\
• 12
00
12.
\
\
02
\
\\
IS
e./
\
\
/4
.'
7'\
§
"e4
'"•
'\,50"
0
05
~
200.4
".,5
.'"
'\,
5",
14
\
9
t;; 7
\ 6. e9\
....
~
(6 fans/Ito)
.... ' ........
'"
(ZIons/ito)
(4 tons/Ito)
1000);------2~------.:...:....:.:::~4~--~
Number of kernels -m- 2 field (x 103 )
Fig. 19. Relation between number of kernels
per unit field area and lOoo-kernel
weight in various varieties grown at
two spacings (Numbers in figure
indicate varieties listed in Table 12)
o 60cm x 60cm
• 30cm x 30cm
~
o
l"'-
\
'.13 10 \
.,'"
o
2
~
\
\
\
I
I
013
./2
O~----~2~~--47-L-A-I--~6------~8--
~ 9
• 30cm x30cm
\
\
03
08
~
\
\
14
-
~
o 60cm x 60cm
\
\
\ -'3
•
06
08
~
I
2
5 •
02
03
'j
5
0-
,..
0 0 /3
0010
II
,
o
4
o
14
o
6
7
0
IS.6
3
o
'i ~
03
0
o
5
o
13
/2 0
2
o
012
o
2
4
6
8
Role of dry motter production (g-m-Z leaf-doy-')
Fig. 21.
Dry matter production after
silking as related to LAI and
rate of dry matter production
per unit leaf area in fifteen
varieties (1969)
(Numbers in figure indicate
varieties listed in Table 12)
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
105
(Fig. 18, bottom). At· 60 em x 60 em, however, there was no correlation
between grain yield and number of kernels per ear.
The correlation between number of kernels per unit field area and grain
yield was significant, including 30 em x 30 em and 60 em x 60 cm. However,
there was no clear relationship between grain yield and lOOO-kernel weight.
There was a loose negative correlation between number of kernels per
unit field area and lOOO-kernel weight (Fig. 19). However, the equi-yield
.10
.9
.7
10
.4
't
./5
.14 . ,
8
~
"~
~
....
"
~
04
.2
~
.8
0/5
.5
6
07
./2
~
06
.13
4
.6
.3
010
09
014
05
08
02
03
0/2
11
01
~ 2
013
0
4
2
0
6
LAI
e/o
e9
~
'~
~
.7
15
~
~
.~
.4
40
.,.
eS
el3
r5
'"t;
.~
3e
~ 20
0,
-t2
03
~
08
.~
'"
."
e5
04
e'
010
07
.~
1':
.,5
.,
~
~
.,
0609
015
014
05
011
e
0/3
60cm x 60cm
o 30cm x 30cm
"-
"
~
~ 0
0
Z
4
6
8
10
12
Number of kernels· dm- 2 leaf
Fig. 22.
Relations between LAI and number of kernels per unit leaf
area (~op) and between number of kernels per unit leaf
area and rate of grain weight increase per unit leaf area
(bottom)
(Numbers in figure indicate varieties listed in Table 12)
106
A. TANAKA AND J. YAMAGUCHI
lines which are composed by assuming grain yield = number of kernels per
unit field area x lOOO-kernel weight, do not fit the observed data. The
observed correlation indicates that the larger the number of kernels per
unit field area, the higher was the grain yield.
The correlation between grain yield and dry matter production after
silking was positive (Fig. 20). The dry matter production during grainfilling was more closely correlated with the rate of dry matter production
per unit leaf area during this growth period than LAI, at least at a given
spacing (Fig. 21).
The po at silking ranged from 27 to 57 mg COz·dm-z·hr- 1 (Table 12).
Varietal difference was, however, statistically significant only at the 10
percent level. The difference of the po between two spacings was highly
significant. No correlation was observed between the rate of dry matter
production per unit leaf area during grain-filling and the po at silking.
The larger the LAI, the smaller the number of kernels per unit leaf
area though there were several exceptions at 30 cm x 30 cm (Fig. 22, top).
There was a positive correlation between number of kernels per unit leaf
area and rate of grain weight increase per unit leaf area (Fig. 22, bottom).
Discussions
There are varietal differences in yielding ability. Positive heterosis in
the grain yield is apparent. New varieties in Hokkaido are hybrids with
a high positive response to dense planting and with high yielding ability.
The seeds or the embryo of a hybrid are not necessarily larger than
its parental inbreds. A heterosis in the po has been reported (HEICHEL
and MUSGRAVE (1969)). Some combinations reported in this paper showed
a heterosis in the po. In other combinations, however, the heterosis was
not statistically significant. Among commercial varieties in Hokkaido, varietal differences in the po were statistically significant only at the 10 percent
level. On the other hand, the growth rate of hybrids was higher from
germination. The higher growth rate results in a higher rate of leaf
expansion. Because of a larger leaf area, the rate of photosynthesis per
plant is higher, and consequently, plant weight is larger in hybrids. Moreover, the time from sowing to silking is shorter, and the grain-filling period
is longer in hybrids. For these reasons, hybrids give a higher grain yield
than their parental inbreds.
These differences indicate the importance of vegetative vigor. Hybrids
are capable of producing a high grain yield even with mediocre cultural
practices of their vegetative vigor. A careful examination is needed to
determine whether vegetative vigor is an indispensable trait for high yielding
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
107
varieties, even with good management.
In rice there is heterosis in vegetative vigor (JENNINGS (1967)). However, it is not necessarily associated with high grain yields under intensive
cultural conditions (] ENNINGS and JESUS (1968), KAWANO and TANAKA
(1969)).
By comparing commercial varieties in Hokkaido, it becomes apparent
that grain yield is positively correlated with dry matter production during
grain-filling. Dry matter production during this growth phase is more closely
correlated with rate of dry matter production per unit leaf area than LA!
at least for a specific planting density. There is no simple correlation
between rate of dry matter production per unit leaf area during grain-filling
and po at silking. Grain yield is more closely correlated with kernel number per unit field area than with lOOO-kernel weight. On unit leaf area
basis rate of grain weight increase is positively correlated with number of
kernels.
These results suggest that the potential photosynthesis of the leaves is
not the limiting factor, but the number of kernels, the sink, is the factor
intimately controlling rate of grain-filling and grain yield.
In rice, there is ample evidence of a positive relation between spikelet
number per unit field area and grain yield. However, this correlation is
more evident at low yield levels. At high yield levels, the percentage of
sterility is an important factor in controlling grain yield. In this instance,
it is the source rather than the sink that is the yield limiting factor.
The concept of the plant type has been well established in rice on the
basis of physiology related to the dry matter production (HAYASHI and ITo
(1961), TSUNODA (1965), TANAKA, KAWANO and YAMAGUCHI (1966)).
There are several reports on maize indicating the importance of plant
type. The importance of erect leaves was demonstrated by PENDLETON,
SMITH, WINTER and JOHNSTON (1968). The association between leaf display
and dry matter production had been studied on the basis of light interception by the leaves and response of po to light intensity (LOOMIS, WILLIAMS,
DUNCAN, DOVRAT and NUNEZ (1968)). On the basis of these studies,
simulation analyses are being developed (DUNCAN, LOOMIS, WILLIAMS and
HANAU (1967)).
Removing tassels increases grain yield, especially at close spacings. This
is explained by the tassels shading the leaves (DUNCAN, WILLIAMS and
LOOMIS (1967), HUNTER, DAYNARD, HUME, TANNER, CURTIS and KANNENBERG (1969)). However, competition for photosynthetic products (CHINWUBA,
GROGAN and ZUBER (1961)) or for nitrogen (SANFORD, GROGAN, JORDAN
A. TANAKA AND J. YAMAGUCHI
108
and SARVELLA (1965)) between the developing ears and the tassels or the
pollen is also considered to be one of the causes of a positive effect of
detasseling or male sterility on the grain yield.
Although these reports indicate the importance of plant type in maize,
the experiments reported in this paper did not support the view that leaf
display is important in relation to the grain yield in maize.
V. CULTURAL FACTORS AFFECTING GRAIN YIELD
In the previous chapter it was demonstrated that the number of kernels
per unit field area, the sink, is the key factor controlling varietal difference
in yielding ability. In addition to this varietal difference, grain yield and
various traits of a variety are influenced by cultural conditions.
The objective of this chapter is to find out the key traits which control
the fluctuation of grain yield of a variety caused by cultural conditions such
as climatic condition, fertilizer level and spacing. Interactions between
varietal characteristics and cultural conditions were also discussed.
Date of Planting
Fukko No.8 was sown on four dates at two-week intervals (on May
1, 15, 29, and June 12 in 1970) (TANAKA and HARA (1971b)). These
sowing dates were designated treatments No. I, No, II, No. III, and No. IV,
TABLE 13.
Effect of planting date on various
plant traits (Fukko No.8, 1970)
Treatment No.
Date of sowing
I
II
III
IV
May 1
May 25
May 29
June 12
Days
From
To
Sowing-Emergence
20
17
15
12
Emergenee-Silking
71
69
61
58
Silking-Harvest
67
58
54
46
244
241
203
3.61
Plant height* (em)
239
LA1*
4.39
4.57
4.46
Grain yield (tons/ha)
9.21
9.04
7.97
4.96
Grain: total weight ratio
0.58
0.53
0.46
0.35
Kernel number per m 2 fiield (X10 3)
3.36
3.15
3.02
3.02
lOOO-kernel weight (g)
274
284
264
164
*
Maximum value during growth.
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
109
respectively. All plots were harvested on October 6 because of a heavy
frost.
The later the sowing, the fewer the days from sowing to emergence
and from emergence to silking (Table 13). This was an effect of differences
in temperature at sowing. Though the interval from sowing to silking was
short.er in later sowings, the date of silking was earlier and the interval
from silking to harvest was longer in the earlier sowings than in later ones.
The rate of dry matter production for two months following sowing
was higher in later sowings, but then the rate was almost the same in all
sowings (Fig. 23, top). The total plant weight at harvest was greatest for
treatment No. III and smallest for No. IV.
No.J![
15
'"
~
]'"
10
....-<:
.!'1>
~ 5
§
Q:
040
#'
(~'SiIM",)
-::..
60
80
100
120
Doys offer sowing
16(}
140
6~
J).~.~
20
1
~.
oNolV
Wo,J[
jL;;
-No.1
t
Si/king
-20
0
20
40
60
Days offer silking
Fig. 23.
Changes of plant weight and sugar content in
the culm during growth as influenced by date
of sowing (Fukko No.8, 1970)
110
A. TANAKA AND J. YAMAGUCHI
There was a more rapid increrse in sugar content of the culm after
silking for treatment No. III than for No. I. This indicates a better balance
between photosynthesis of the leaves and starch formation in the kernels
for treatment No. I than for No. III.
The plant height and the LAI were largest for No. II and decreased
with delay in sowing (Table 13). The grain yield and the ratio of grain:
total plant weight were highest for treatment No. I and decreased with a
delay of sowing, especially from treatment No. III to No. IV. The number
of kernels per unit field area and the lOOO-kernel weight decreased with
a delay of sowing, especially from treatment No. III to No. IV.
Interactions among Spacing, Nitrogen Level and Variety
Two dent corn lines, OH43 x OH45 and D403 x D405, were tested. Combinations of three nitrogen levels (0, 100 and 300 kg N/ha) and
three spacings (25 cm x 25 cm, 50 cm x 50 cm and 75 cm x 75 cm) gave nme
TABLE
~
-"
14.
Effect of spacing and nitrogen level on grain
yield, amount of nitrogen absorbed and some
plant traits in two lines (1967)
Line
Spacing (em)
D403xD405
OH43xOH45
N level (kg/ha)
Grain yield
(tons/ha)
Nitrogen absorbed
(kg N/ha)
Plant height
(em)
Thickness of culm
(g·m- 1)
LAI
25x25
I
50x50
I
75x75
25x25
I
50x50
I
75x75
0
3.01
3.79
2.34
5.18
5.12
3.42
100
6.13
5.13
2.92
8.03
6.80
3.74
300
7.14
5.63
2.55
10.65
7.30
4.44
0
66
70
77
74
65
70
100
125
145
115
124
171
94
300
155
111
114
163
185
139
216
0
151
176
166
191
227
100
190
187
170
243
253
236
300
209
189
170
265
251
239
0
18
59
70
13
39
75
100
23
67
84
21
59
78
300
29
63
80
24
54
81
0
3.37
1.65
0.82
3.59
1.52
1.00
100
4.88
2.05
0.92
5.34
1.99
0.88
300
5.77
1.48
0.89
6.25
2.09
0.95
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
III
treatments (TANAKA, YAMAGUCHI and FUJITA (1969)).
Silking was earlier in D403 x D405 than in OH43 x OH45 and was
earlier at wide spacings than at close spacings.
The grain yield of D403 x D405 was higher than that of OH43 x OH45
(Table 14). The higher the nitrogen level or the closer the spacing, the
higher was the grain yield in both varieties.
Nitrogen increased the plant height, especially at close spacings. At close
spacings with no nitrogen the plants were short because of a nitrogen
deficiency. Culm thickness, expressed as the weight per unit culm length,
increased markedly with an increase in spacing and increased much less
with the addition of nitrogen. The LAI was larger at close spacings and it
increased with an increase of nitrogen application at close spacings.
With no nitrogen application, about 70 kg N/ha was absorbed regardless
of lines or spacings. This indicates the amount of nitrogen that was
available from the soil. At close spacings with no nitrogen, plants suffered
15.
TABLE
"-
Effect of spacing and nitrogen level on
yield components in two lines (1967)
Line
Spacing (cm)
OH43x OH45
N
,
(kg/ha)
1st
ear
Percentage
of plants
having
I
2nd
ear
Row number per
cob
Kernel number per
m 2 field (x1Q3)
1000-kernel weight
(g)
I
-
25x25
I
50x50
I
D403xD405
75x75
25x25
I
50x50
I
75x75
0
75
100
100
100
100
100
94
100
100
100
100
100
300
100
100
100
100
100
100
0
0
0
18
0
0
58
100
100
0
0
19
0
0
38
300
0
0
16
0
0
71
0
13.7
15.0
15.3
13.6
14.5
14.6
100
14.3
15.3
15.1
13.8
15.3
14.6
300
14.8
14.7
14.3
15.0
14.7
14.8
0
2.32
100
4.22
300
4.07
1.04
2.89
1.89
2.40
1.29
4.13
2.46
1.30
2.75
1.18
4.72
2.72
1.56
1.84
1.16
0
136
216
238
188
285
309
100
153
225
238
205
290
303
300
184
215
228
238
282
299
A. TANAKA AND J. YAMAGUCHI
112
seriously from nitrogen deficiency. The higher the nitrogen level, the larger
the amount of nitrogen absorbed by the plants.
There were no barren plants except in the plot of OH43 x OH45 at
25 cm x 25 cm with no nitrogen application (Table 15). Second ears formed
at 75 cm x 75 cm, but they did not produce many kernels. The number of
rows per cob is almost constant except for a slightly lower value with no
nitrogen application at 25 cm x 25 cm. The number of kernels per row was
larger at wide spacings or at high nitrogen levels. The number of kernels per unit field area increased with a decrease of spacing and with an
increase of nitrogen application. The 1000-kernel weight increased with an
increase of spacing and with an increase of nitrogen application, especially
at 25 cm x 25 cm. Grain yield was positively correlated with dry matter
production after silking (Fig. 24).
1>20
025-300
10
/125
1>30
{j.4Q
025-101}
,.30
so-,ooo
&4iJ
"'SO
•
05O-J08
2S-JDO
2S
.sO-DOO·.
.60
.. 2S-0
420
50
075-3111
50-0e 75-0
o
.'00
075-100
.'5-300
.75-/80
15-0. AIOO
.25-0
• OH43 x OH45
o 0403 x 0405
'" Fukko No_ 8
.. Go/den Cross Bantam
~~--------~5----------/~0--------~~7---
Dry matter production after silking ( ton / ho)
Fig. 24.
Relation between dry matter production after silking
and grain yield (Numbers in figure are: For example,
20-200 means 20 em X 20 em with 200 kg N/ha, and
20 means 20 em X 20 em)
In a separate experiment, two varieties, Fukko No.8 and Golden Cross
Bantam, were tested at nine spacings from 10 cm x 10 cm to 100 em x 100 cm
(TANAKA, YAMAGUCHI and YAMAGAMI (1970)).
The plants at 10 cm x 10 cm and 15 cm x 15 cm lodged seriously before
tasseling and were discarded. Since plants in plots with closer spacings
than 30 cm x 30 cm tended to lodge at about silking, they were supported
artificially.
TABLE
Variety
Spacing
(cm)
25.3
Kernel number per ear
:;0
><
Golden Cross Bantam
s::::
;»
>-l
>-l
ttl
JJ
TPW
(tons/ha)
Ear number
per m 2
tJ
20X20 j25X25j30X30 j40X40 j50X50 j60X60 jlOOXl00 20x20 j25X25j30X30 140X40 150X50 I60X60 IlOOX100
11.66
lOOO-kernel
weight
(g)
Kernel
number per
m 2 (X 103)
Effect of spacing on grain yield (GY), total plant
weight (TPW) and yield components in Fukko No.8
and Golden Cross Bantam (1968)
Fukko No.8
GY
(tons/ha)
GY/TPW
16.
10.36
9.82
9.28
7.55
6.00
2.29
4.84
5.09
7.36
4.64
6.71
4.85
3.99
j
ttl
t""
21.0
18.4
16.2
12.8
10.2
4.1
13.3
13.2
14.4
12.9
11.8
11.0
7.9
tJ
n
o
0.40
0.43
0.47
0.50
0.52
0.52
0.49
0.31
0.34
0.45
0.46
0.35
0.39
0.45
s::::
'1J
o
Z
195
213
226
243
278
298
299
178
195
213
226
234
231
230
--6.00
4.86
4.34
3.82
2.71
2.01
0.77
6.3
4.0
3.0
1.2
2.72
ttl
Z
>-l
(fJ
2.61
3.45
2.97
1.98
2.10
1.74
;»
Z
8.1
7.3
6.4
3.2
(l
:;0
tJ
20.3
13.4
11.0
17.5
12.1
12.2
;»
296
361
394
605
671
670
621
156
216
283
356
273
330
337
Z
j
ttl
Barren plant
percentage
19
Tiller number
per m 2 *
25
14
1
0
0
0
0
30
24
0
0
0
0
0
-
- -
tJ
o>rj
16
ILl
6.3
4.0
2.8
1.0
25
16
ILl
12.0
11.7
10.8
5.3---
Tiller number
per plant*
t""
1
1
------
* Including the main culm.
1
1
1
1
1
1
1
1
1.9
2.9
3.9
5.3
s::::
2::
N
tTl
..
I-'
I-'
W
114
A. TANAKA AND J. YAMAGUCHI
Silking was August 7 and 15 for Fukko No. 8 and Golden Cross
Bantam, respectively. The closer the spacing, the later was the silking.
The difference in the silking date between 100 cm x 100 cm and 20 cm x
20 cm was 8 days in Fukko No.8 and 4 days in Golden Cross Bantam.
Harvest was October 5-8, about 150 days after sowing.
The grain yield at 100 cm x 100 cm was higher for Golden Cross Bantam
than for Fukko No. 8 (Table 16). However, at closer spacings, Fukko No. 8
yielded more than Golden Cross Bantam and the difference became larger
as plant population increased. The grain yield of Fukko No.8 continued
to increase with a decrease of spacing to 20 cm x 20 cm. In contrast, the
yield of Golden Cross Bantam reached a maximum at 30 cm x 30 cm and
then decreased with a further decrease of spacing.
The number of ears per unit field area increased with a decrease of
spacing. At wide spacings it was larger for Golden Cross Bantam than for
Fukko No.8 because Golden Cross Bantam formed tillers. The difference
became smaller with a decrease of spacing and at close spacings the difference was reversed because there was a higher percentage of barren plant in
Golden Gross Bantam. Even at wide spacings, there was rarely more than
one well developed ear on a culm in either variety.
The number of kernels per ear remained almost constant between
100 cm x 100 cm and 50 cm x 50 cm. The number was larger for Fukko
No. 8 than for Golden Cross Bantam. It decreased with a decrease of
spacing below 50 cm x 50 cm for Fukko No.8. For Golden Cross Bantam,
however, it was lower at 50 cm x 50 cm than at 40 cm x 40 cm and below
40 cm x 40 cm it decreased with a decrease of spacing. The lower value at
50 cm x 50 cm was due to many small ears on tillers.
The number of kernels per unit field area increased with a decreased
spacing for Fukko No.8. For Golden Cross Bantam, it increased with
a decrease of spacing, reached a maximum at 30 cm x 30 cm and then
decreased with a further decrease of spacing. The 1000-kernel weight
was greater for Fukko No.8 than for Golden Cross Bantam and it decreased
with a decrease of spacing in both varieties.
For Fukko No.8, the closer the spacing, the greater the total dry
matter production, the greater the grain yield and the smaller the ratio of
grain: total plant weight. For Golden Cross Bantam, a decrease of spacing
did not always result in an increase of the total plant weight. The ratio
of grain: total plant weight of this variety was smaller than that of Fukko
No.8.
The LAI was larger at closer spacings (Fig. 25). At 10 cm x 10 cm at
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
/5
Fukko No.8
115
Go/den Cross Bantam
10
Jacm x JOcm
J5cm x J5cm
30cm x 30cm
Mcm x 60cm
/DDem x IDDem
/oocm x IDDem
90
110
90
110
130
Oays offer sowing
Fig. 25
Changes of LAI with growth at various
spacings in two varieties (1968)
80 days after sowing when lodging became serious, the LAI reached 15 in
both varieties. At wider spacings, Golden Cross Bantam had a larger LAI
than Fukko No.8 due to tillering ability. The LAI increased with growth
and reached a maximum at about silking. The leaves of Fukko No.8
remained green longer after silking than those of Golden Cross Bantam.
Death of the lower leaves was more rapid at close spacings.
There was a positive correlation between grain yield and dry matter
produlction after silking in both varieties (Fig. 24). The crop growth rate
(CGR) increased with an increase of LAI and there was no optimum LAI
in either variety until silking (Fig. 26). After silking CGR of Fukko No.8
continued to increase as plant population and LAI increased, but in Golden
Cross Bantam there was an optimum LA! at about 4 to 5. This indicates
that the efficiency of leaves in dry matter production was almost the same
for both varieties during early growth stages, but after silking a varietal
difference was apparent. The efficiency remained high in Fukko No.8,
but it decreased in Golden Cross Bantam, especially at closer spacings.
The percentage nitrogen content of the shoot was lower, but the amount
of nitrogen absorbed by the plants was greater at close spacings than at
116
A. TANAKA AND J. YAMAGUCHI
wider spacmgs (Table 17). These results show that at close spacmgs less
nitrogen is available per plant than at wider spacmgs .
..
///,,,,,,
40
//
/////
..
/
/
"'",- 30
///
~
..
~
/
/"
o.
6.
~-::=:.-=-=
~~o.
/ _~o
/,,!.~
~
~
0
,':(~
::::. 20
,(/0
'"
",,-" ec,"'"
,{/ 0
~
~ "',
.R
t;
! /,
•
0
,
•
,
I DR
I 0"
II
',,,
Days after sowing
from- to
--+-
51 - 63
--«-
64 - 91
--..--
92 - 118
Solid symbol, thin line: Fukko No.8
Open symbol, thick line ; Golden Cross Bantam
;-
°O~--~2~---4~----6~--~8~---/~O~--~/2~
LAI
Fig. 26.
TABLE
Relation between LAI and crop growth rate at
successive stages of growth (Fukko No.8 and
Golden Cross Bantam, 1968)
17.
Nitrogen content of shoot and amount of
nitrogen absorbed by the plants as affected
by spacing in Fukko No. 8 (F 8) and Golden Cross Bantam (GCB) (1968)
80 days after sowing
Growth stage
Spacing
(cm)
N (%)
F 8
I
GCB
Silking
N absorbed
(kg/ha)
F 8
I
N absorbed
(kg/ha)
N (%)
GCB
F 8
I
GCB
F 8
I
GCB
lOx10
2.54
3.99
92
118
-
-
-
-
15x15
3.02
3.93
73
87
-
-
-
-
20x20
3.54
4.01
73
74
1.95
2.64
182
257
25X25
3.82
3.77
52
48
2.03
2.57
176
215
30X30
3.62
4.15
35
41
1.94
2.38
169
190
40X40
3.66
4.27
23
27
2.23
2.61
131
170
50x50
3.74
4.19
15
19
2.27
2.83
114
160
60x60
3.66
4.26
14
10
2.27
3.32
98
150
100x100
3.89
4.14
4
5
2.38
3.26
41
91
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
117
Interactions between Climatic and Cultural Conditions
A nitrogen level x phosphorus level x spacing experiment using Fukko
No.8 was conducted in a field of National Hokkaido Agricultural Experiment Station in 1968 and in 1969 (TANAKA, YAMAGUCHI and HARA
/,-""~,
(p ~
20
~//
E
I~
I
';'::0°<:::1/
I
\.,,/ L
~
~
..,1::
_0-;
p-7
10
~
~"1----o//IJ69
:I
1
~
I
~o
-'~'O-><
,,_
,
I '
\
'\
1
,fC,
II
I 0--_0
•
6...:-- ------ 95 days ----------*---- -60days - - - ,J 1968
."
May
Fig. 27.
2
101 days
June
July
:>.,.
August
39 days
1969
September
October
Climatic conditions during growth and duration of
each growth phase (Fukko No.8, 1968 and 1969)
.------.
/t=-=--================.
......-----.---------------------.
~
1968 1P69
30cm x 30cm
40cm x 40cm
60cm x 60cm
0
•
A
0
...
•
°O~----I~OO~--------~30~O
O~---,JO~O~--------~~---------5T,omo
Nitrogen level (kg N/ho)
Phosphorus level (kg ROs/ha)
Fig. 28.
Effect of nitrogen and phosphorus application on
grain yield (Fukko No.8, summarized figure)
118
A. TANAKA AND J. YAMAGUCHI
(1971b)). The soil is volcanic ash origin and is low in phoshorus. Twentyseven treatments were chosen. These were the factorial combinations
of three nitrogen levels (0, 100 and 300 kg N/ha), three phosphorus levels
(0, 100 and 500 kg PzOs/ha) and three spacings (30 em x 30 em, 40 em x 40 em
and 60 em x 60 em). For convenience, the treatment of 30 em x 30 em with
100 kg N/ha and 500 kg PzOs/ha, for example, is designated as 30D . lOON .
500P. Sowing was made May 7-8, 1968, and May 19-20, 1969.
The 1968 weather was favorable and at 40D . lOON . lOOP it took 95 days
for the vegetative phase and 60 days for the grain-filling phase (Fig. 27).
In 1969, sowing was 10 days later than in 1968 and growth was delayed
because of low temperatures, especially in June. At 40D·100N . lOOP, it
took 101 days for the vegetative phase and only 39 days for grain-filling.
10
8
6
4
~ 2
~
~
?j
~
~
00
.~ 10
.:::
~
zoo
100
Amount of nitrogen absorbed (kg N/ho)
8
t:.
/).
o
4
o
t:.
t:.
6
/
;OD.~~
.~
y.
0
...
2
....
",..
•
1968 1909
••••
• •••• ••
00
10
0
30cm x 30cm 0
40cm x 40cm to.
60cm x 60cm [J
20
•
'"
•
30
Amount of phosphorus absorbed (kg P/ho)
Fig. 29.
Relation between amount of nitrogen or phosphorus absorbed
by plants and grain yield (Fukko No.8, 1968 and 1969)
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
119
In both years, silking tended to be later with dense planting, especially with
no nitrogen application. Phosphorus application hastened silking in 1969.
In 1968, grain yield increased with a decrese of spacing at 300N
(Fig. 28). However, at low nitrogen levels it was lower at 30D than at
wider spacings. The effect of phosphorus application was small and was
observed only at 30D. In 1969, grain yield was smaller, the effect of
phosphorus was larger and the effect of nitrogen was smaller.
The amount of nitrogen and phosphorus absorbed by the phants IS
positively correlated with grain yield in a given year (Fig. 29). The efficiency of nitrogen or phosphorus absorbed by the plants in grain production
is different between 1968 and 1969. With 30D· 300N· OP in 1969, the
o
10
o
o
8
A
A
0
}
6
4
.
1:i2
~
......
• • •
..
...... ..
••
•
'~"
~O
~ 0
"'~!O
1 2 3
.s.
1':
C.!)
8
30cmx 30cm 0
40cm x 40cm A
60cm x 60cm 0
o
A
o
1968 1909
5
4
Number of kemels· ni2 field (x 103)
o A
4,
..
•
6
4
••• ..
....
•
o
o
<{l
o
0
0
0
2
00
100
200
300
!OOO-kernel weight (g)
Fig. 30.
Relation of grain yield to number of kernels per unit field
area and to lOOO-kernel weight (Fukko No.8, 1968 and 1969)
A. TANAKA AND J. YAMAGUCHI
120
efficiency of nitrogen was extremely low. However, it was improved by
a phosphorus application as indicated by the arrow in the figure.
There was a close correlation between number of kernels per unit field
area and grain yield in a given year, except for plots at closer spacings
with low nitrogen application (Fig. 30, top). There was a remarkable difference in the 1000-kernel weight between these two years. The low 1000kernel weight in 1969 was the cause of the low grain yield (Fig. 30,
bottom).
With the data collected from the experiments described above in which
Fukko No.8 was grown under various cultural conditions, a loose negative
correlation was demonstrated between number of kernels per unit field area
and 1000-kernel weight for each experiment (Fig. 31). The equi-yield lines
drawn in the figure indicate that the larger the number of kernels per field
area the higher was the grain yield.
300
~\
\
I
\
I
a
0
A
\
\
..
\
_.
\ .
\
-:..
\
\
\
\
A
"
~
00.,
\
\
Normal plots
.
... P deficient plots )1909 (Dpt. station)
\
\
\
3200
> (
• \
\
:
• Spacing bpt. 1968 (HoM. Univ.)
0 Normal plots
t·
~. N deficient plots 1908 bpt. sto /O(1)
\
I
~~_·o 0·","-
---............
.,~
'-',
'-...
\
g~"
""
\
\
\
l1
A'"
\06....
l:J.
:
""...
'" .... ,
'4,
I::::. ' .....
...:.\
...
-... .............
-- ---
....
",-
\\.
\
Ll
...
.....
"'(Btans/ho)
6
",
'
....
.... ....
---- (4 tons/hoy
------- (lion/ho)
°O~--------~2----------~4~---------6~
Number of kernels·m'2 field (x 10 3 )
Fig. 31.
Relation between number of kernels per unit field
area and lOOO-kernel weight in Fukko No.8 under
various cultural conditions
For the spacing experiment at Hokkaido University in 1968 an increase
plant population with adequate fertilizer resulted in an increase of grain
yield. The increase was derived mainly from an increase of the number
of kernels. In this case, the 1000-kernel weight decreased with a decrease
of spacing, but this decrease did not compensate for the increase of kernel
number. In the case of the experiment at National Hokkaido Agricultural
10
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
121
Experiment Station in 1968, a take-off from the above mentioned correlation,
however, was observed when nitrogen was limiting. When nitrogen deficiency
became serious at close spacings, the number of kernels as well as the
lOOO-kernel weight decreased and the grain yield decreased. When phosphorus level was low in this experiment in 1969 with adverse climatic conditions,
the lOOO-kernel weight was low due to a delay in silking.
An increase of LAI caused by an increase of planting density or of
nitrogen application generally resulted in a decrease of number of kernels
per unit leaf area (Fig. 32, top). However, at a given LAI the number
0
14
00
•
"
o
.'"
0
00
LI
D
"
00
6
'"
"'" •'" ...
'"
•
0
0
"
AMl
o.
• •.
...
_.60.°
LI LI
: .. • •...
••
o
£10
0
•
o
•
...
LAI
o
00
o
• Siociflg bpt. fP68 (Hokk. Ufliv.)
o NOImol plots
I
• N deficient plots IP68 ,bpt. sto.)
" Normal plols
t
... P deficient plots 1969 bpt. So.)
>
> (
.
o
•
oo '"
o
£I
o
£I
•
•
•... £l• LI
....
~
...
A
NlJmber of kernels· dm'2 leaf
Fig. 32.
Relations between LAI and number of kernels per
unit leaf area (top) and between number of kernels
per unit leaf area and rate of grain weight increase
per unit leaf area (bottom)
122
A. TANAKA AND J. YAMAGUCHI
was less when the plants were deficient in nitrogen. In addition to this
tendency there was a trend that the larger the number of kernels per unit
leaf area, the higher was the rate of grain weight increase per unit leaf
area (Fig. 32, bottom).
Discussions
If the season is favorable, the duration of grain-filling is about 55 days
though there are varietal differences ranging from 53 days to 61 days
(HILLSON and PENNY (1965)). Extending grain-filling to 55 days increases
lOOO-kernel weight. Late sowing or low temperatures during the vegetative
growth phase delay silking and result in a short grain-filling period. Dense
planting, especially with a low nitrogen level, delays silking. Phosphorus
application hastens silking, especially with low temperatures.
The LAI can reach 15 at very close spacings and with adequate fertilizer, but with such a large LAI, the plants lodge. Provided that there is
no lodging, the CGR increases with an increase of LAI, at least during
vegetative growth. Although the net assimilation rate (NAR) decreases
with an increase of the LAI, there is no optimum LAI and above a certain
LAI the CGR is kept constant. An asymptotic relation between the LAI
and the CGR has been reported (WILLIAMS, LOOMIS, and LEPL Y (1965b)).
The major determinant of CGR is reported to be solar radiation intercepted
by the population until tasseling (WILLIAMS, LOOMIS, DUNCAN, DOVRA T
and NUNEZ (1968)). After silking, the situation becomes quite different. In
high-yielding varieties like Fukko No.8, there is no optimum LAI, even
above a LAI of 8. For low-yielding varieties like Golden Cross Bantam,
there is an optimum LAI between 4 and 5 above which the CGR decreases.
There is also a report indicating that rice varieties with low yielding
ability have an optimum LAI of 6. However, for varieties with high
yielding ability, there is no optimum LAI, but a ceiling LAI of about 6
(YOSHIDA (1969)).
At wide spacings, nitrogen application has only a limited effect on the
LAI unless the nitrogen level in the soil is very low. This applies particularly to non-tillering varieties. Under these conditions, nitrogen application
increases nitrogen content of the leaves which may result in an increased
NAR (NUNEZ and KAMPRATH (1969)). Conversely, at close spacings, nitrogen frequently becomes the leaf expansion limiting factor. Then, nitrogen
application increases the LAI as well as the nitrogen content of the leaves.
The increase of nitirogen content, however, does not necessarily increase
the NAR.
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
123
For a given grain-filling duration, grain yield is more closely correlated
with the number of kernels per unit field area than with the lOOO-kernel
weight. This suggests that the CGR during grain-filling is closely controlled
by the number of kernels.
The number of kernels per unit field area is the product of the number
of ears per unit field area and the number of kernels per ear.
The number of kernels per unit field area tends to be smaller when
the vegetative phase is less than 80 days.
The number of ears per unit field area increases with a decrease of
spacings provided with adequate nitrogen. At close spacings, the percentage of barren plants increases. Nitrogen deficiency is one reason for this.
Varieties which actively tiller produce more than one ear per plant at wide
spacings. Limited information described above suggests that at close spacings
active tillering varieties may have a higher barren plant percentage.
The number of kernels per ear is the product of the number of rows
per ear and the number of kernels per row. For a given variety, the
number of rows is constant under a wide range of cultural conditions and is
under genetic control. The number of kernels per row decreases with a
decrease of spacing and nitrogen level.
It has been reported that at close spacings where mutual shading is
a problem, the activity of nitrate reductase tends to be low and the plants
utilize nitrate in the soil poorly. For this reason, it has been argued that
high nitrate reductase activity is a desirable varietal character (ZIESERL,
RIVENBARK and HAGEMAN (1953)). Differences in the activity of this
enzyme between parental inbreds and their hybrids have been discussed
(SCHRADER, PETERSON, LENG and HAGEMAN (1966)). However, the results
obtained from experiments reported here demonstrate that a low nitrogen
percentage in the plants at close spacing is a result of the increased demand
for the nitrogen available from the soil and not a decrease in the ability
of the plants to absorb and utilize nitrogen. At close spacing, the plants
usually absorbed more nitrogen per unit field area than at wide spacing.
Lodging limits the possibilities for combining close spacing with an
adequate supply of nutrients. However, the maximum grain yield can
be obtained under such combinations. The relation between lodging and
potassium nutrition has been reported by LIEBHARDT and MURDOCK (1965).
However, in the experiments reported here, the potassium content of the
shoot remained high, even at close spacings. It is very necessary to find
out how far the spacing can be decreased without lodging by using lodging
resistant varieties and with reasonable cultural method.
124
A. TANAKA AND J. YAMAGUCHI
VI. GENERAL DISCUSSIONS
The experiments described in this paper indicate that there are similarities between maize and rice. However, there are also several important
differences which affect the measures needed to improve yield. These are:
1) Tillering is the characteristic which, more than any other, enables
rice to respond to changes in cultural conditions. This facility is absent or
weak in maize. Also, rice has smaller leaves but more of them than maize.
These characteristics give rice wider adaptability than maize to changes in
cultural conditions.
2) The maximum LAI reported under experimental condition is 20 for
maize (WILLIAMS, LOOMIS and LEPLEY (1965a)) and 12 for rice. However,
with a LAI of above 10, both crops generally lodge.
3) The rate of photosynthesis per unit area of newly developed healthy
leaves is 60-80 mg CO2 • dm -2. hr- l for maize and 30-40 mg CO2 • dm -2. he l
for rice. Also, translocation of photosynthetic products from the leaves is
faster and more efficient in maize than in rice. Even so, good grain yields
under experimental conditions in Hokkaido are 8 to 10 tons/ha of maize
and 6 to 8 tons/ha of rice. Why then is the difference in the grain yield
less than might be expected from so large difference in the photosynthetic
rates?
4) The top three leaves on a culm in rice and the five leaves at or
above the ear in maize are the most important for providing photosynthetic
products to the developing grains. Translocation of photosynthetic products
from these leaves to the kernels is upward in rice and downward in maize.
5) The vegetative growth of rice stops at flowering and active grainfilling starts after flowering. Some starch or sugars accumulate in the
leaf-sheath or in the culm until flowering and they are then translocated to
the grains after flowering. In maize, the vegetative growth overlaps the
initial grain-filling phase for about two weeks after silking. There is no
measurable starch accumulation in the vegetative organs and there is only
a very limited accumulation of sugars in the culm.
6) The efficiency of respiration in dry matter production during grainfilling is higher in maize than in rice. In maize, the lower strata of the
crop canopy do not consume a large amount of the photosynthetic products
from the upper leaves by their respiration. In rice, the respiratory loss in
the lower strata accounts for a relatively large proportion of the products of
photosynthesis, at least under some conditions.
7) In rice, the plant type is important in efforts to improve yield.
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
125
However, in maize, observations on the leaf arrangement, the plant height,
etc. did not give any evidence to demonstrate the relationship between
yielding ability and plant type.
8) A reasonably good grain yield of 7 tons/ha can be obtained with
the following combinations of yield components.
Ear number
per m 2 field
Rice
Maize
400
4
Grain number
per ear
70
700
Grain number
per m 2 field
lOOO-grain
weight (g)
28000
25
2800
250
These figures illustrate big differences in the number of grains per unit
field area and the lOOO-grain weight for obtaining equal grain yields.
9) In both crops, the greater the production of dry matter after
flowering, the higher the grain yield. The dry matter production during
this growth phase can be considered in terms of the relation between source
and sink. A breakthrough in the present yield level seems likely to come
from an improvement of the source in rice and from an improvement of
the sink in maize.
The relationships shown in these experiments described in this paper
between grain yield and its separate components indicate that it is the
number of kernels per unit field area, more than any other factor, that determines the grain yield of maize.
The number of kernels per unit field area, the sink size, is composed
of (1) number of plants per unit field area, (2) number of ears per plant and
(3) number of kernels per ear.
1) Number of plants per unit field area is under the control of
cultivation method. It can be increased by increasing the planting density.
The plant population required for high yield appears to be larger in rice
than in maize.
2) Number of ears per plant is the product of number of culms per
plant and average number of ears per culm. Rice produces more tillers and
more ears, especially at wide spacings, than maize. In rice, the number of
ears per plant is the product of number of culms per plant and percentage
of ear bearing culms. Both components decrease with a decrease of spacing,
but the number of ears per unit field area always increases with a decrease
of spacing. In maize at wide spacings, varieties that tiller may produce
several tillers bearing at least one ear and in some varieties there may be
more than one ear on a culm. Consequently, the number of ears per
plant is larger at wide spacings. However, this does not compensate for
the decrease in plant population. Also, the ears on tillers are frequently
126
A. TANAKA AND J. YAMAGUCHI
small and the second ear on a culm generally does not produce many
kernels. Thus, at wide spacing, the grain yield is usually small, even with
multi-ear varieties. The number of ears per unit field area can be increased
most easily by increasing plant population. The percentage of barren plant
then limits the number of ears per unit field area. The percentage of
barren plants is higher when nitrogen is limiting and it is likely to be
higher in active tillering varieties than varieties which produce few tillers.
3) Number of grains per ear in rice is the product of number of
spikelets per ear and percentage of filled grains. With a decrease of spacing,
both of these components decrease. With an increase of nitrogen level,
number of spikelets increases and the percentage decreases. In maize the
number of kernels per ear is the product of number of rows per ear and
number of kernels .per row. The number of rows is a genetic character
which is not easily affected by cultural conditions. The number of kernels
per row decreases with a decrease of spacing and nitrogen level. There
are varietal differences in the number of kernels per row and also in the
response of the number to cultural conditions.
The product of these three components, namely the number of grains
per unit field area, generally increases with an increase of planting density
in rice and maize provided all nutrients, especially nitrogen, are adequately
supplied. Increasing the planting density and the level of nitrogen, the
LAI increases and the number of grains per unit leaf area decreases. This
decrease appears to be more significant in maize than in rice.
One more point to be mentioned is the potential size of grains. In
rice, the husk, which limits grain size, is determined during spikelet development. It is not yet known whether the potential size of kernels of maize
is determined before silking or later.
These discussions demonstrate the importance of discussing the dry
matter production during grain-filling in relation to the number of kernels.
It follows that; (a) a high grain yield can be obtained if the dry matter
production during grain-filling is large; (b) the dry matter production during
this growth phase is the product of duration of grain-filling and crop growth
rate; (c) if the duration is less than 55 days, there is a close correlation
between the duration and the lOOO-grain weight, hence the grain yield; and
(d) the CGR increases with an increase of LAI provided the increase of
LAI accompanies a reasonable increase of the number of kernels: However,
(e) an increase of LAI generally causes a decrease of the number of kernels
per unit leaf area and (f) this decrease of the sink size per unit leaf area
results in a decrease of the rate of dry matter production per unit leaf
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
127
area, namely the rate of grain weight increase per unit leaf area.
Thus, the key for a higher grain yield is maintaining a large number
of kernels per unit leaf area combined with a large LAI. For this purpose
maintaining a high percentage of ear bearing plants and a large number of
kernels per ear at close spacings is critical.
CONCLUSION
From the foregoing discussions, the following conclusion can be drawn.
The potential rate of photosynthesis of the leaves is much higher for
maize than for rice, but the difference in the grain yield is comparatively
small. This is because the rate limiting factor of the dry matter production
after flowering, which is closely correlated with the grain yield, is the "sink"
in maize and is the "source" in rice at least at present yield levels. In maize,
the limitation in the sink size interferes with the expression of potential
photosynthetic capacity. In rice the solar radiation available to the plant
and the respiratory loss from the lower strata of the crop canopy limit the
expression of the sink size.
For this reason, the plant type which controls the efficiency of utilization of solar energy for dry matter production is important to improve
rice grain yields, but not so important for maize. In maize, the sink size,
the number of kernels per unit field area, is the key factor controlling grain
yield.
Sufficient nitrogen with close plant spacing are the cultural conditions
needed for a high grain yield. Under these conditions the leaf area index
increases, but the number of kernels per unit leaf area decreases. This is
the reason why the sink frequently limits the grain yield of maize.
Uniculm with one large ear having many rows of many kernels are
desirable characteristics for high-yielding maize varieties. At close spacings,
the percentage of barren plants and the number of kernels per row are the
major factors limiting sink size. Physiology related to such factors should
be studied more to improve cultural methods and varieties of maize.
A closer spacing than a critical one is not practical for farmers because
under such conditions plants become susceptible to lodging. Breedging lodging resistant varieties is obviously important.
Varieties and cultural methods that provide 80 days for the vegetative
growth and more than 55 days for ripening are prerequisites for high grain
yields.
128
A. TANAKA AND J. YAMAGUCHI
ACKNOWLEDGMENT
The authors wish to gratefully mention that this study was partially
sponsored by a grant from the Rockefeller Foundation and also by Science
Research Grant of the Ministry of Education, Japan. They express sincere
thanks to Dr. P. R. GOLDSWORTHY, Plant Physiologist, and Mr. D. C. BORK,
English language editor, of the International Maize and Wheat Improvement
Center, Mexico, for technical and English editing, respectively. They wish
to mention with thanks that the seed materials were supplied by Mr. A.
KUWAHATA, Breeder's Stock Farm, Hokkaido Central Agr. Expt. Stat., the
data cited in this paper were collected by Messrs. Y. HAY AKA WA, K. Fu JIT A,
T. HARA and others and the manuscript of this paper was typed by Miss
S. ARISUE.
REFERENCES
ALLISON, J. C. S. and WEINMANN, H. 1970. Effect of absence of developing grains
on carbohydrate content and senescence of maize leaves. Plant Physiol. 46,
435-436.
ARASHI, K. 1954. Studies on growth of the leaves of paddy rice plants. II. Seasonal
changes of starch content in the leaf, sheath. Proc. Crop Sci. Soc. Japan 23,
25-27 (in Japanese with English summary).
ASANUMA, K., NAKA, J. and TAMAKI, K. 1967. Effect of topping on the growth, the
translocation and accumulation of carbohydrates in corn plants. Proc. Crop
Sci. Soc. Japan 36, 481-488 (in Japanese with English summary).
BAKER, D. N. and MUSGRAVE, R. B. 1964. Photosynthesis under field conditions. V.
Further plant chamber studies of the effects of light on corn (Zea mays L.).
Crop Sci. 4, 127-131.
CHINWUBA, P. M., GROGAN, C. O. and ZUBER, M. S. 1961. Interaction of detasseling,
sterility, and spacing on yields of maize hybrids. Crop Sci. 1, 279.
CORNELIUS, P. L., RUSSELL, W. A. and WOOLEY, D. G. 1961. Effect of topping on
moisture loss, dry matter accumulation, and yield of corn grain. Agron. J. 53,
285-289.
DUNCAN, W. G., HATFIELD, A. L. and RAGLAND. J. L. 1965. The growth and yield of
corn. II. Daily growth of corn kernels. Agron. J. 57, 221-223.
DUNCAN, W. G., LOOMIS, R. S., WILLIAMS, W. A. and HANAU, R. 1967. A model
for simulating photosynthesis in plant communities. Hilgardia 38, 181-205.
DUNCAN, W. G., WILLIAMS, W. A. and LOOMIS, R. S. 1967. Tassels and productivity
of maize. Crop Sci. 7, 37-39.
EARLEY, E. B. 1952. Percentage of carbohydrates in kernels of Station Reid Yellow
Dent Corn at several stages of development. Plant physiol. 27, 184-190.
EASTIN, J. A. 1970. C-14 labelled photosynthate experiment from fully expanded
corn (Zea mays L) leaf blades. Crop Sci. 10, 415-418.
DRY MATTER YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
129
HA YASH I, K. and ITO, H. 1961. Studies in rice varieties with particular reference to
the efficiency in utilizing sunlight. I. The significance of extinction coefficient
in rice plant communities. Proc. Crop. Sci. Soc. Japan 30, 329-333 (in Japanese
with English summary).
HANWAY, J.]. 1963. Growth stages of corn (Zea mays L.). Agron. J. 55, 487-492.
HEICHEL, G. H. and MUSGRAVE, R. B. 1969. Varietal differences in net photosynthesis
of Zea mays L. Crop Sci. 9, 483-486.
HESKETH, J. D. 1963. Limitations to photosynthesis responsible for differences among
species. Crop Sci. 3, 493-496,
HILLSON, M. T. and PENNY, L. H. 1965. Dry matter accumulation and moisture loss
during maturation of corn grain. Agron.]. 57, 150-153.
HOYT, P. and BRADFIELD, R. 1962. Effect of varying leaf area by partial defoliation
and plant density on dry matter production in corn. Agron. J. 54, 523-525.
HUNTER, R. B., DAY NARD, T. B., HUME, D. J., TANNER, J. W., CURTIS, J. D. and
KANNENBERG, L. W. 1969. Effect of tassel removal on grain yield of corn
(Zea mays L.). Crop Sci. 9, 405-406.
ISHlZUKA, Y. 1965. Nutrient uptake at different stages of growth. The mineral
nutrition of the rice plant. Johns Hopkins Press. p. 199.-217.
ISHlZUKA, Y. and TANAKA, A. 1953. Biochemical studies on the life history of rice
plants. ]. Sci. Soil and Manure, Japan 23, 113-116 (in Japanese).
JENNINGS, P. R. 1967. Rice heterosis at different growth stages in a tropical environment. International Rice Comm. Newsletter 16, 24-26.
JENNINGS, P. R. and JESUS,]. 1968. Studies on competition in rice. I. Competition
in mixture of varieties. Evolution 22, 119-124.
KAWANO, K. and TANAKA, A. 1969. Vegetative vigor in relation to yield and nitrogen
response in the rice plant. Japanese. J. Breeding 19, 277-285.
KIESSELBACH, T. A. 1948. Endosperm type as a physiologic factor in corn yields. J.
Amer. Soc. Agron. 40, 216-236.
LIEBHARDT, W. C. and MURDOCK, T. J. 1965. Effect of potassium on morphology
and lodging of corn. Agron.]. 57, 325-328.
LOOMIS, R. S., WILLIAMS, W. A., DUNCAN W. G., DOVRAT, A and NUNEZ, F. A. 1968.
Quantitative descriptions of foliage display and light absorption in field communities of corn plants. Crop Sci. 8, 352-356.
MACK, H. J. 1965. Effect of topping on yield of sweet corn. Proc. Amer. Soc. Hort.
Sci. 86, 411-414.
MATSUSHIMA, S., OKABE, T. and WADA, G. 1957. Analysis of developmental factors
determining yield and yield prediction in lowland rice. XLI. Studies on the
mechanism of ripening. Proc. Crop. Sci. Soc. Japan. 26, 17-18 (in Japanese with
English summary).
Moss, D. N. 1962. Photosynthesis and barrenness. Crop. Sci. 2, 366-367.
Moss, D. N., MUSGRAVE, R. B. and LEMON, E. R. 1961. Photosynthesis under field
conditions. III. Some effects of light, carbon dioxide, temperature and soil
moisture on photosynthesis, respiration and transpiration of corn. Crop Sci.
1, 83-87.
130
A. TANAKA AND J. YAMAGUCHI
Moss, D. N. and PEASLEE, D. E.
age and nutrient status.
MURATA, Y. 1961. Studies on
significance. Bull. Nat!'
1965. Photosynthesis of maize leaves as affected by
Crop Sci. 5, 280-281.
the photosynthesis of rice plants and its cultural
Inst. Agr. Sci (Japan). D 9, 1-169 (in Japanese with
English summary).
MURATA, Y. 1964. On the influence of solar radiation and air temperature upon the
local differences in the productivity of paddy rice in Japan. Proc. Crop. Sci.
Soc. Japan 33, 59-63 (in Japanese with English summary).
MURAYAMA, N. et al. 1955. The process of carbohydrate accumulation associated
with growth of rice plants. Bull. Nat!. Inst. Agr. Sci. (Japan). Ser. B 4, 123-166
(in Japanese with English summary).
MURAYAMA, N. 1965. The influence of mineral nutrition on the characteristics of
plant organs. The mineral nutrition of the rice plant. Johns Hopkins Press.
p. 147-172.
NUNEZ, R. and KAMPRATH, E. 1969. Relationship between N response, plant population, and row width on growth and yield of corn. Agron. J. 61, 279-282.
PALMER, A. F. E. 1969. Translocation pattern of 14C-Iabelled photosynthate in the
corn plant (Zea mays L.) during the ear-filling stage. Ph. D. Thesis, Cornell
Univ.
PENDLETON, J. W., SMITH, G. E., WINTER, S. R. and JOHNSTON, T. J. 1968. Field
investigations of the relationships of leaf angle in corn (Zea mays L.) to grain
yield and apparent photosynthesis. Agron. J. 60, 422-425.
RAGLAND, J. L.. HATFIELD, A. L. and BENOIT, G. R. 1965. The growth and yield of
corn. I. Microclimatic effects on the growth rate. Agron. J. 57, 217-220.
REEN, VAN R. and SINGLETON, W. R. 1952. Sucrose content in the stalks of maize
inbreds. Agron. J. 44, 610-614.
SANFORD, J. 0., GROGAN,C. 0., JORDAN, H. V. and SARVELLA, P. A. 1965. Influence
of male-sterility on nitrogen utilization in corn, Zea mays L. Agron. J. 57,
580-583.
SCHRADER, L. E., PETERSON, D. M., LENG, E. R. and HAGEMAN, R. H. 1966. Nitrate
reductase activity of maize hybrids and their parental inbred. Crop Sci. 6,
169-173.
TAKEDA, T. 1961. Studies on the photosynthesis and production of dry matter in the
community of rice plants. Japanese. J. Botany 17, 403-437.
TANAKA, A. 1961. Studies on the nutrio-physiology of leaves of rice plant. J. Faculty
of Agr. Hokkaido Univ. 51, 450-550.
TANAKA A. and FUJITA, K. 1971. Studies on the nutrio-physiology of the corn plant.
(Part 7) Analysis of dry matter production from the source-sink concept. J. Sci.
Soil and Manure, Japan 42, 152-156 (in Japanese).
TANAKA, A. and HARA, T. 1970. Nutrio-physiological studies on the photosynthetic
rate of the leaf. (Part 1) Effect of nitrogen status on the photosynthetic rate in
the corn plant. J. Sci. Soil and Manure, Japan 41, 502-508 (in Japanese).
TANAKA, A. and HARA, T. 1971a. Nutria-physiological studies on the photosynthetic
rate of the leaf. (Part 2) Effect of phosphorus status on the photosynthetic rate
DRY MATTER, YIELD COMPONENTS AND GRAIN YIELD OF MAIZE
in the corn plant.
131
J. Sci. Soil and Manure, Japan 42, 300-303 (in Japanese).
TANAKA, A. and HARA, T. 1971b. Studies on the nutrio-physiology of the corn plant.
(Part 10) Grain yield as affected by planting date.
42, 435-438 (in Japanese).
TANAKA, A. and HAYAKAWA, Y. 1971.
J. Sci. Soil and Manure, Japan
Studies on the nutrio-physiology of the corn
plant. (Part 8) Nutrio-physiological studies on heterosis. J. Sci. Soil and Manure,
Japan, 42, 237-242 (in Japanese).
TANAKA, A. and ISHIZUKA, Y. 1969. Studies on the nutrio-physiology of the corn
plant. (Part 2) Development of the growth phases and accumulation of elements
and carbohydrates associated with the development.
J. Sci. Soil and Manure,
Japan 40, 113-120 (in Japanese.)
TANAKA, A., KAWANO, K. and YAMAGUCHI, J. 1966.
Photosynthesis, respiration, and
plant type of the tropical rice plant. International Rice Research Institute,
Tech. Bull. 7, p. 46.
TANAKA, A. and MORISADA, N. 1971. Studies on the nutrio-physiology of the corn
plant. (Part 9) Varietal traits associated with the grain productivity.
J. Sci. Soil
and Manure, Japan 42, 304-308 (in Japanese).
TANAKA, A., NAVASERO, S. A., GARCIA, G. V., PARAO, F. T. and RAMIREZ, E. 1964.
Growth habit of the rice plant in the tropics and its effects on nitrogen
response. International Rice Research Institute, Tech. Bull. 3, p. SO.
TANAKA, A. and YAMAGUCHI,]. 1968. The growth efficiency in relation to the growth
of the rice plant. Soil Sci. and Plant Nutr. 14, 11(}-116.
TANAKA, A. and YAMAGUCHI, J. 1969.
Studies on the growth efficiency of crop
plants. (Part 1) The growth efficiency during germination in the dark.
J. Sci.
Soil and Manure, Japan 40, 38-42 (in Japanese).
TANAKA, A., YAMAGUCHI, J. and FUJITA, K. 1969.
Studies on the nutrio-physiology
of the corn plant. (Part 3) Effect of nitrogen application and spacing to dry
matter production and grain yield. J. Sci. Soil and Manure, Japan 40, 498-503
(in Japanese).
TANAKA, A., YAMAGUCHI. J. and HARA, T. 1971a.
Studies on the nutrio-physiology
of the corn plant. (Part 6) Respiratory rate and dry matter production during
the growth.
]. Sci. Soil and Manure, Japan 42, 85-88 (in Japanese).
TANAKA, A., YAMAGUCHI, ]. and HARA, T. 1971b. Studies on the nutrio-physiology
of the corn plant. (Part 11) Grain yield as affected by fertilizer level, planting
density, and climatic condition. ]. Sci. Soil and Manure, Japan 42, 465-470 (in
Japanese).
TANAKA, A., YAMAGUCHI, ]. and IMAI, M. 1971. Studies on the nut rio-physiology
of the corn plant. (Part 5) Fluctuation of photosynthetic rate during the growth.
]. Sci. Soil and Manure, Japan 42, 33-36 (in Japanese).
TANAKA, A., YAMAGUCHI, ]. and YAMAGAMI, M. 1970. Studies on the nutrio-physiology
of the corn plant. (Part 4) Response to planting density of two varieties.
Sci Soil and Manure, Japan 41, 363-368 (in Japanese).
TOGARI, Y, et al. 1954.
rice plant.
J.
Studies on the production and behavior of carbohydrate in
1. Changes of principal constituents in each organ accompanied
132
A. TANAKA AND J. YAMAGUCHI
with its development. Proc. Crop Sci. Soc. Japan 22, (3-4) 95-97 (in Japanese).
TSUNODA, S. 1965. Leaf characters and nitrogen response. The mineral nutrition of
the rice plant. Johns Hopkins Press p. 401-418.
UCHIJlMA, Z., UDAGAWA, T., HORIE, T. and KOBAYASHI, K. 1967. Studies of energy
and gas exchange within crop canopies. (1) CO 2 environment in a corn plant
canopy. J. Agr. Meteor. (Japan) 23, 99-108 (in Japanese with English summary).
VERDUIN, J. and LOOMIS, W. E. 1944. Absorption of carbon dioxide by maize. Plant
Physiol. 19, 278-293.
WAGGONER, P. E., Moss, D. N. and HESKETH, J. D. 1963. Radiation in the plant
environment and photosynthesis. Agron. J. 55, 36-39.
WILLIAMS, W. A., LOOMIS, R. S., DUNCAN, W. G., DOVRAT, A. and NUNEZ, F.A.
1968. Canopy architecture at various population densities and the growth and
grain yield of corn. Crop Sci. 8, 303-308.
WILLIAMS, W. A., LOOMIS, R. S. and LEPLEY, C. R. 1965 a. Vegetative growth of
corn as affected by population density. 1. Productivity in relation to interception of solar radiation. Crop Sci. 5, 211-215.
WILLAMS, W. A., LOOMIS, R. S. and LEPLEY, C. R. 1965 b. Vegetative growth of
corn as affected by population density. II. Components of growth, net assimilation rate, and leaf area index. Crop Sci. 5, 215-219.
WRIGHT, J. L. and LEMON, E. R. 1966. Photosynthesis under field conditions. IX.
Vertical distribution of photosynthesis within a corn crop. Agron. J. 58,
265-268.
YAMAGUCHI, J., HARA, T. and TANAKA, A. 1970. Studies on the growth efficiency
of crop plants. (Part 2) The growth efficiency of corn plant at successive stages
of growth. J. Sci. Soil and Manure, Japan 41, 73-77 (in Japanese).
YOSHIDA, S. 1969. Growth rate and plant characters of rice varieties in relation to
their response to nitrogen application. Paper presented at the 11th Intern'l
Bot. Congress.
YOSHIDA, S., COCK, J. N. and PARAO, F. T. 1971. Physiological aspect of high
yields. Symposium on rice breeding. The International Rice Research Institute,
Sept. 6-10, 1971 (Mimeograph).
ZIESERL, J. F., RIVENBARK, W. L. and HAGEMAN, R. H. 1953. Nitrate reductase
activity, protein content and yield of four maize hybrids at various plant
population. Crop Sci. 3, 27-32.